Hello Avery,
We found that it’s the issue in WordPress 6.4.3 and will be fixed in version 6.4.4, you can check the core ticket for this at https://core.trac.wordpress.org/ticket/60398. So for now, if anyone has an issue like this then first install this “Force using PclZip” plugin and then all the zip installation will work.
To install Force using PclZip Plugin
1. Download the plugin zip file from https://github.com/aaronjorbin/force-pclzip/archive/refs/tags/0.1.zip
2. Go to “Plugins => Add New => Upload Plugin”, then browse and locate the plugin zip file you have downloaded
3. Click on “Install Now” and then Activate the plugin.
After this, you can upload the theme zip file from “Appearance => Themes => Add New => Uploads”
Regards,
Sakin