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C:\Users\memememe>nslookup amathotspot.net 9.9.9.9
Server: dns9.quad9.net
Address: 9.9.9.9
*** dns9.quad9.net can't find amathotspot.net: Non-existent domain
Do you have a static entry in this environment for this domain?
I think OP configured the hotspot feature. In that case the domain used for hotspot does not need to really exist, can be anything syntactically correct.
Yes, but the phone must be using the hotspot server for DNS, could be that the phone has a different DNS server configured, or the hotspot server / router has DNS remote requests disabled