Can my PSU support my GPU?

[codeschnitz]

PSU: Thermaltake Litepower 550w
GPU: Sapphire R7 250 1 GB GDDR5
CPU: AMD A10 7860k

Before using Thermaltake Litepower 550W, I was using a generic 700W psu, My GPU and CPU works together quite well with it, but I changed it due to short cable problem.

So, bought a Thermaltake Litepower 550W, now my problem is, my computer will shut off, mouse, keyboard, and monitor suddenly don't work. But my cpu, gpu, and fans still runs.

I now can't use my GPU because whenever I do, I can't use my computer.
Then, after a couple hours of using my computer, upon inserting my GPU, it will suddenly work.
The problem comes back whenever my computer had a couple hours of rest (it's completely shutdown).

And oh, I use a generic AVR (the very old school one), I don't own a UPS, I don't even know what it's VA rating or does it have any. Or how it would affect the my PSU.

Please help me out.

 

[Nikola_35]

R7 250 is not power hungry it doesnt even require power connector so your gpu is compatible with that psu, but maybe you have faulty psu

 

[codeschnitz]

R7 250 is not power hungry it doesnt even require power connector so your gpu is compatible with that psu, but maybe you have faulty psu

Thank you so much for your reply, I'm sorry that it takes me so long to respond, because there's this reCaptcha loop was stuck in.
Anyway, I kinda don't want to go back to the store if I'm not sure what's really going on with my PSU, I don't know too if they can run tests in there with it.
Also, I'm wondering if a UPS or AVR can affect the PSU performance, because I just have a generic one, that may be limiting it.

 

[Nikola_35]

I dont think it has anything to do with UPS, when is that happening when its under heavy load or just randomly?
sorry it took me long to respond

 

[codeschnitz]

I dont think it has anything to do with UPS, when is that happening when its under heavy load or just randomly?
sorry it took me long to respond

The problem only happens after my computer has rested/ cooled down.
I never had a problem even under heavy load, and it doesn't happen randomly.
For it to work, it (pc core temp) needs to heat up first. So whenver I'm going to use my PC in the morning, I will remove the GPU then I will need to use the computer for an hour or so without it, then put the GPU back in. Then after that, it will work just fine.