Probably not going to happen. I don’t want to be hard on you, or say things that might frustrate you, but it really ISN’T Manjaro’s FAULT. In fact, it has nothing to do with Manjaro.
See, the AUR is Arch (Linux) User Repository. Not Manjaro User Repository. Also, the packages you find in the AUR isn’t created by the Manjaro, or even Arch Linux official team members, but by the U sers. Yeah, sure, there are packages there that’s maintained by some of the Manjaro team members, but it’s not official, otherwise it wopuld probably have been in the repositories.
That mirror has been decommissioned AFAIK.
It won’t. Because the AUR isn’t a Manjaro or even Arch Linux server. It’s jusst a repository of recipes, to put it like that. And those packages, those ingredients, are downloaded from all over the internet.
Some other server(s) might also be decommissioned or even just changed a bit, so that It looks like the machine is gone, to pamac. So the global refresh probably did that for you and that’s why the official repositories are now working.
Try removing that file locally, to force a download of a newer one:
sudo rm /var/tmp/pamac-build-<username>/packages-meta-ext-v1.json.gz
<username> is the name of your actual user on the PC.