The problem is probably made worse by trying to use a UST tyre with a Stans rim.
The No Tubes rims are designed so you can use a normal tyre, with slacker tolerances, to convert to tubeless, with some latex to seal the sidewalls. A UST rim/tyre is designed to work as an airtight system, with the associate tighter tolerances. No Tubes rims do work just fine with UST tyres though. Use some something slippery, like very soapy water, to help the tyre slide up the rim profile.
If you're using rim strios, not yellow tape, this will make the problem much, much worse.
I've had several tyres over the years refuse to seat fuilly, even at 60PSI, this has always been fixed with soapy water, occasionally I need to pull the tyre up with my hand, but this has maybe happened once or twice and only when I didn't use enough soapy water.
Good luck - and make sure that young childern are removed from the room before yiu start to protect them from the swearing!