I am not able to export in Media Encoder

You haven't provided any information other than the error, and the error says the source couldn't be found. Have you moved the source files your project is referencing or deleted the temporary AME files after you sent the project to the AME but before you started encoding? Please provide a lot more information about what you're doing and whether this just happens on one project, one composition, or just with GIFs.

As a test, have you tried exporting the same comp directly from the Render Queue to a format like ProRes?