I had the same issue with my viewsonic years ago which btw cost me over 1k. It's PSU died from always running too hot (discolored PCB). It started off just randomly turning off every now and then and got more frequent to the point it wouldn't power up any more.
I replaced some caps and burnt resistors and it worked for another month before something on the main board died. I sold it for scrap parts.
Even when the monitor was in warranty they couldn't replace it like for like or of a similar sized monitor, it was a 28" and they stopped making 28" with 24" now being the biggest (at the time), I refused to accept smaller. They didn't even have spares for it so I couldn't even fix it.
Last time I ever touched their products. Didn't even last the 2 years so very disappointing the least to say.