Working on Arc Pro 3.5.1, I just tried to add an SRTM I just downloaded, and it loaded a grey square. I am not sure why.
Possibly may need to Calculate Statistics (Data Management)—ArcGIS Pro | Documentation
How big is the area? 1 tile or multiple? if multiple, if you click/inspect some cell values, do they show as different values?
Any more info and screenshots wouldn't hurt either.