Did that. Also removed and re-added one extension from EM entirely, and reset the same handset to defaults. It wouldn’t register until I manually edited the password in the phone GUI itself.
Also changed that extension from ChanSIP to PJSIP, switched the ChanSIP and PJSIP ports to defaults (the original system was installed before PJSIP existed), and everything else I could think of. Eventually rolled back to v13 and opened a ticket. Very frustrating afternoon.