I had the same issue last year. When I called Jamf Support, they suggested that I do the upload using a private browser. That worked. 

Just tried that and still no luck.  Thanks for the suggestion!!

I uploaded a new PublicKey and then downloaded another new Device Token and that seems to have work!!

My post from last year has a response that may help. 

https://community.jamf.com/t5/jamf-pro/quot-the-file-received-was-not-valid-quot-error-while-importing-a/td-p/233830 

@hodgesji suggested something that may solve your issue.

Great! I had just replied letting you know about something that someone suggested to me when I had this problem. He suggested the same thing.

Worked! Thanks

I appreciate that many people are posting back that uploading a new JSS Public Key to ASM is the accepted solution, but I've not found additional information about whether there are OTHER CONSEQUENCES to uploading the new public key.  If I do this will I need to update/renew any other tokens or anything besides the Apple Device Enrollment tokens (which is what brought me here in the first place.... "file not valid" error.)

Can someone confirm that replacing the Jamf public key in ASM had no other consequences and resolved ONLY this problem?

I have had to do this several times while working as a contractor recently for a company that has over 700 Jamf Pro servers. We didn't see any issues with doing this.

this worked for me! ty

:( No love for my attempts