Hello unknowndomain,
According to your description, I did the same test on my side and the result shows that the logo displayed normally. Regarding to your problem, I suggest you change another browser like Microsoft Edge or Chrome and then upload the logo again to see whether
it works.
If the issue still persists, please contact another administrator to help you change the logo and check it other administrators can upload the logo normally.
Welcome back to share the result with me and I will do my best to help you.
Regards,
Seven