If you have entered any data with a non existent HSN code, this warning error is flashed. At the time of uploading GSTR-1, portal does not check the HSN codes and accept the return. However, while uploading GSTR-9, validity of HSN codes is checked by portal. You cannot upload GSTR-9 with invalid HSN codes.
You should check these HSN codes on goolge (hint: search “find hsn code”). If they are non-existent, you should find and correct the HSN code. If you get a false warning w.r.t. HSN code, the same may be intimated to Catpro support team.
This check is implemented in Visual Catpro version 1705.42 (dated 06/08/2019).