Membership category - do you mean Member level or something else?

One idea is to re-check the spelling: create a few member records by hand with the appropriate levels and then in the export file you can copy-paste from these dummy records into the ones you want to update.

Also, it shows errors - what specific errors? (During import you can download a file which will contain your newly imported file with error messages spelled out for each record - did you look at those?)