Having issues with Gate Start....

When setting up the T7 at a gate I'm getting several issues..

First I'm getting the HYD PRESS DEM C1 & 2 messages that I'm unable to resolve.

Second when starting the GSX push back I remove the wheel chocks which disconnects ground power and everything goes haywire with alarms and messages and everything shutting off. I have the APU switched on at least 10 mins before disconnecting ground power.

Third I'm unable to start the engines on push back or any time thereafter. Probably related to my two previous issues.

I can program my imported FP via PFPX and have no issues at all with the FMC setup and have been using this YouTube video as a guide:

I haven't had much luck resolving my issues with the manuals and desperately need a ramp start guide from a gate.

I'm also not entirely sure if I'm having issues with either my system or the T7 install so this is only adding to my confusion.

Finally are the checklists necessary for a proper start and config as for troubleshooting I've been skipping them to test my gate startup.

Thanks!