500 Error - Issues with MarketPress and FrameMarket

I'm installing the FrameMarket and MarketPress based on this how to from your site:

https://premium.wpmudev.org/forums/topic/how-to-build-your-own-etsy-like-site-using-marketpress

When I get to step five and I try to go to the user's Dashboard it gives me a Error. I'm not quite sure why.

Here's what it says:

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Apache Server at carvestock.com Port 80

Any ideas?

Gordon