This just happened to me last night. I couldn't figure out why I couldn't make a call as of last night and this morning when I went to my VoIPo control panel I noticed my credentials reset. I too am using an Obihai ATA. Specifically Here is the message I get in the BYOD area;

"Unfortunately we have not verified that your device is currently provisioned and registered to VOIPo's network, please ensure your device is currently connected and registered in order to retrieve your softphone SIP credentials!"

and in the devices area of the control panel;

"You do not currently have any devices registered to our servers!"

The weird thing is, in about 20 minutes I can go back to the control panel and everything will show fine. OBIHAI ATA will show up under devices and the BYOD area will show the credentials. As soon as I try to make a call on the phone the BYOD area and the Devices area of the control panel will show the errors above. Wait awhile and they'll go back. Been happening all morning.