Problem with pdb upload

Hello, I have problem with uploading of my pdb and error is: Error in PDB file. No atom data have been found for chain A, please check that the chain ID is present in your PDB file. Do you know how to solve this problem? When I open the pdb everything is OK so I do not understand why is this happening. I am starting to be frustrated because of that.

Thank you!!!

Did you open the PDB file as a text file? Does it contain chain A?