I have a client who set up his page many years ago with the basel theme but they lost contact with the service provider and now the theme cannot be updated because they don’t have the credentials
In this case I would like to recommend purchase new license and update the theme to the latest version. Also if you purchase the license you will get 6 month author support from the theme author. otherwise try to collect the purchaser account credentials so that you can get access for the theme update download.
Okay, yes, because the error it tells me is this: An error occurred while updating Basel: The package could not be unzipped. PCLZIP_ERR_BAD_FORMAT (-10): Unable to find End of Central Dir Record signature