If your .crt opens as readable text and starts with "-----BEGIN CERTIFICATE-----", you can typically use it as .pem by renaming it.
Steps:
1) Confirm it is PEM-encoded (see the verification steps below).
2) Make a copy of the file for safety.
3) Rename the file extension from .crt to .pem.
- Windows: Right-click > Rename. If extensions are hidden, enable ""File name extensions"" in File Explorer's View menu first.
- macOS/Linux: Rename in Finder/File Manager, or run: mv yourcert.crt yourcert.pem
4) Upload the .pem to your service and test.
If renaming fails or your service still rejects the file, verify the format and convert if needed.