We're sorry about the experience with Photoshop due to the option to Save As PNG being missing from the menu. Would you mind checking if you are working on a 32-bit document or a CMYK document? If you are, please change that to a 16-bit or an 8-bit RGB file by going to the Image menu, then Mode to check if that helps.
That should be happening! Would you mind confirming if you are using Save As or Save a Copy? Or is the option to save the file an a PNG is not available in either of the options? Which version of Photoshop are you working on?
If you are on the latest version of Photoshop (22.4.1) & the option to save the file as PNG is not available in Save a Copy, you can try to reset the preferences of Photoshop using the steps mentioned here: https://adobe.ly/2Qzc0K3