AT&T 1820 answering machine not working with VOIP adapter
I have an old AT&T 1820 telephone / answering machine (circa 1995) which works well on my landline and reliably answers after 4 rings.
I recently switched to VoIP service, with a Grandstream HT802 adapter. The telephone works with the adapter, but the answering machine is somehow not detecting the ring cycles properly and never picks up.
The "cadence" for the primary ringtone sent by the adapter is set to 2000/4000 (2 sec on, 4 sec off) which is the US standard. I tried tweaking that slightly up/down with no effect. Are there any other parameters that might affect the answering function?