Error: File upload failed. Refresh the page using CTRL+R (or CMD+R) and try again.

[stevennt]

MateCat started normally without any problem but I encountered with below error while uploading file for translation:

Error: File upload failed. Refresh the page using CTRL+R (or CMD+R) and try again.

This error shows on the browser at the file upload. No error logs in the console.
What could be wrong?
Tks.

[Mikelpineiro2024]

same problem

[SaraRydin]

Did any of you find a solution? I get the same error today, four years later...