Is this a genuine OBiBT dongle, from Obihai, or are you attempting to use some other brand of WiFi dongle? Only the Obihai dongles will work.
If it IS an Obihai OBiBT, then, did it work correctly with your old router? I've had trouble, myself, when trying to reconfigure an OBiBT to a new WiFi access point. It's unclear why this happens. It seems like you need to completely wipe out any old data about that dongle on your OBi. I went nuts trying to do this, but eventually got it to work.
While the OBi is connected via Ethernet, try logging on to your OBiTALK dashboard, then click on your OBi and get into Expert configuration mode. Find and expand the section for WiFi Settings. Remove all four check marks from the SSID and password fields. Enter your WiFi SSID and password. Scroll down and click Submit. After the device reboots, check those two fields to confirm that the change "stuck", and it didn't get changed back to the wrong value.
Next, log into your OBi's local web page interface (press ***1 on your attached telephone to hear the IP address). Find the same WiFi setting, and confirm that it is correct. If necessary, remove the check marks for the "Default" boxes. Look up at the top of the web page for the section called "Basic settings". Make sure that "Enable" is check-marked, and that it is set to use Access Point 1 as the preferred access point. Make changes as needed and click the submit button to save.