UPS to work with Unifi UDM pro

I am having issues getting a couple of UPS to work with the UDM Pro. Anyone know where I can find out the factors around the power?

Will UDM Pro work with UPS that don’t have a pure sine wave? at the moment that is the only thing I can think of as to why they wouldn’t work - any thoughts?

I have a UDM Pro hooked up to an APC BR1000MS and it isn’t complaining.
It was $100 from Tiger Direct during seasonal sales between (US) Thanksgiving and xmas.
It isn’t hooked up for nut yet as I just brought it online last weekend and I haven’t yet configured a Pi there for nut. they’re now over $200 on and $195 on B&H.