Issue with png files?

[Chief]

Screenshot_20240329_161135.png (13.84 KiB) Viewed 5867 times

As you can see it was under 5mb, in fact I kept reducing it in size first from 5, then 4.7, 4.5 and finally 4.4 which still gave the error (I even tried going out of edit post mode and then going back in just in case there was a weird cache issue), so I gave up and attached the image as a jpg.