email randomly stopped

I don't know if I'm in the right place, but I'm out of ideas. I am not tech-savvy in this area at all, so any help would be appreciated. The company I work for is small, and we don't have tech support or have anyone running our emails; we maintain it all.
Our company emails have stopped sending and receiving, and are bouncing back with 550 "no such user here". No changes were made on our end when this happened.
We have a domain hosted with Network Solutions. The Nameserver DNS says it's Cloudflare, but I don't have any login info for Cloudflare. I can't verify my account because every verification sends an email to an email address that does not receive emails. I can't submit a request on chat, because I can't log in, again, no email to verify, and I can't find any sort of contact info for Cloudflare.
When I try to verify my domain through Google admin, it routes me to Clourdflare, which I can't log into.
At this point I'm going in circles and don't know what to do next or how to contact Cloudflare. Any ideas?
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