Denied access to page

Hi guys
I’m setting up a network, using WP Ultimo for the plans/payments part and more. However, when I click ‘select plan’ in the frontend, it takes me to the page in the screenshot, giving me the message: ‘Sorry, you are not allowed to access this page’. I have deactivated all plugins, except WPUltimo, and that didn’t do the trick. Would you guys have any idea as to why this happens?
Thanks a lot.

best regards,