1. please confirm if your ONT management by U2000 and bind VAS profile, if bind VAS profile, when the OLT detect ONT reset to factory setting , it will download the previous configuration automatically , you can pull out the fiber and reset it again .
2. from OLT command can reset it ,also
huawei(config-if-gpon-0/3)#ont factory-setting-restore
{ portid<U><0,3> }:0
{ all<K>|ontid<U><0,63> }:0
Command:
ont factory-setting-restore 0 0
Are you sure to set the ONT(s) to factory configuration? (y/n)[n]: y
3. replace one new ONT make same test to confirm if this ONT damaged .