Can you shoot me an email to <snip> with your domain information?
I'll forward it where I can and hope we can figure out what's going on.
I unfortunately can promise anything, but I'll try my hardest!
Disc: I work at Google, but not near Domains.
EDIT: removed email as I got the info I needed!
But I'd have to say that it is absolutely shameful that desperate businesses have to try and hope to get noticed on social media to get a problem resolved. We all know that this is true. Not having responsive customer support is the way a scam operates, not a legitimate business.
Offer a paid customer support line if you must to reduce requests to a manageable number, but Google is absolutely killing off many innocent small businesses with the way they operate. Especially in these troubled economic times, it's absolutely horrific behavior.
FWIW, in the case of a domain, this might be an ICANN breach (if OP's domain is a gTLD) or a registry breach (if it's a ccTLD). You HAVE TO be contactable and you HAVE TO reply. If you don't comply to the rules Google Domains might in theory lose its accreditation.
Disc: I work for Google, but my opinions are my own.