proSites paypal express checkout button redirects to the subscription page

hi,

ive got a similar problem like this: https://premium.wpmudev.org/forums/topic/prosites-paypal-checkout-not-working

when i chose a plan and klick on checkout with paypal i just get redirected to the subscription site...

this is the checkout form:

<form autocomplete="off" method="post" action="http://mydomain.com/subscription-plans/?bid=36"><table width="100%" id="psts_checkout_grid"><tbody><tr class="psts_level_head"><th>Level</th><th>Monthly</th><th>Every 3 Months</th><th>Every 12 Months</th></tr><tr class="psts_level level-4"><td valign="middle" class="level-name"><h3>Platinum</h3></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="4:1"> <input type="radio" value="4:1" id="psts-radio-1-4" class="psts-radio" name="psts-radio"> <label for="psts-radio-1-4"> <span class="pblg-price">$160.00</span> <span class="psts-equiv">Try it out!</span> <span class="psts-equiv">You can easily upgrade to a better value plan at any time.</span> </label></div></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="4:3"> <input type="radio" value="4:3" id="psts-radio-3-4" class="psts-radio" name="psts-radio"> <label for="psts-radio-3-4"> <span class="pblg-price">$430.00</span> <span class="psts-equiv">Equivalent to only $143.33 monthly</span><span class="psts-equiv">Save $50.00 by paying for 3 months in advance!</span> </label></div></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="4:12"> <input type="radio" value="4:12" id="psts-radio-12-4" class="psts-radio" name="psts-radio"> <label for="psts-radio-12-4"> <span class="pblg-price">$1,535.00</span> <span class="psts-equiv">Equivalent to only $127.92 monthly</span><span class="psts-equiv">Save $385.00 by paying for a year in advance!</span> </label></div></td></tr><tr class="psts_level level-3"><td valign="middle" class="level-name"><h3>Gold</h3></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="3:1"> <input type="radio" value="3:1" id="psts-radio-1-3" class="psts-radio" name="psts-radio"> <label for="psts-radio-1-3"> <span class="pblg-price">$80.00</span> <span class="psts-equiv">Try it out!</span> <span class="psts-equiv">You can easily upgrade to a better value plan at any time.</span> </label></div></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="3:3"> <input type="radio" value="3:3" id="psts-radio-3-3" class="psts-radio" name="psts-radio"> <label for="psts-radio-3-3"> <span class="pblg-price">$220.00</span> <span class="psts-equiv">Equivalent to only $73.33 monthly</span><span class="psts-equiv">Save $20.00 by paying for 3 months in advance!</span> </label></div></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="3:12"> <input type="radio" value="3:12" id="psts-radio-12-3" class="psts-radio" name="psts-radio"> <label for="psts-radio-12-3"> <span class="pblg-price">$765.00</span> <span class="psts-equiv">Equivalent to only $63.75 monthly</span><span class="psts-equiv">Save $195.00 by paying for a year in advance!</span> </label></div></td></tr><tr class="psts_level level-2"><td valign="middle" class="level-name"><h3>Silver</h3></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="2:1"> <input type="radio" value="2:1" id="psts-radio-1-2" class="psts-radio" name="psts-radio"> <label for="psts-radio-1-2"> <span class="pblg-price">$40.00</span> <span class="psts-equiv">Try it out!</span> <span class="psts-equiv">You can easily upgrade to a better value plan at any time.</span> </label></div></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="2:3"> <input type="radio" value="2:3" id="psts-radio-3-2" class="psts-radio" name="psts-radio"> <label for="psts-radio-3-2"> <span class="pblg-price">$110.00</span> <span class="psts-equiv">Equivalent to only $36.67 monthly</span><span class="psts-equiv">Save $10.00 by paying for 3 months in advance!</span> </label></div></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="2:12"> <input type="radio" value="2:12" id="psts-radio-12-2" class="psts-radio" name="psts-radio"> <label for="psts-radio-12-2"> <span class="pblg-price">$380.00</span> <span class="psts-equiv">Equivalent to only $31.67 monthly</span><span class="psts-equiv">Save $100.00 by paying for a year in advance!</span> </label></div></td></tr><tr class="psts_level level-1"><td valign="middle" class="level-name"><h3>Bronze</h3></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt opt-selected"> <input type="hidden" value="1:1"> <input type="radio" value="1:1" id="psts-radio-1-1" class="psts-radio" name="psts-radio"> <label for="psts-radio-1-1"> <span class="pblg-price">$2.00</span> <span class="psts-equiv">Try it out!</span> <span class="psts-equiv">You can easily upgrade to a better value plan at any time.</span> </label></div></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="1:3"> <input type="radio" value="1:3" id="psts-radio-3-1" class="psts-radio" name="psts-radio"> <label for="psts-radio-3-1"> <span class="pblg-price">$55.00</span> <span class="psts-equiv">Equivalent to only $18.33 monthly</span> </label></div></td><td style="width: 23%" class="level-option"><div class="pblg-checkout-opt"> <input type="hidden" value="1:12"> <input type="radio" value="1:12" id="psts-radio-12-1" class="psts-radio" name="psts-radio"> <label for="psts-radio-12-1"> <span class="pblg-price">$190.00</span> <span class="psts-equiv">Equivalent to only $15.83 monthly</span> </label></div></td></tr></tbody></table> <input type="hidden" value="1" name="period" id="psts_period"> <input type="hidden" value="1" name="level" id="psts_level"><div id="psts-paypal-checkout"><h2>Checkout With PayPal</h2> <input type="image" border="0" alt="PayPal - The safer, easier way to pay online!" name="pypl_checkout" src="https://fpdbs.paypal.com/dynamicimageweb?cmd=_dynamic-image&locale=en_US"></div></form>

ive tryed to recreate the checkout site, that worked once and then the same error...

i want to use paypal expres and saved my api information. this error apears with sandbox and live version.

regards
patrick