Turns out it wasn't just the 3600 in registration period (that was my guess). A few more settings are needed that I would have never guessed.
In the Service Providers section:
Under ITSP Profile x General:
1) Name = PhonePower
2) DTMFMethod = Auto
3) X_UseFixedDurationRFC2833DTMF = not checked
4) DigitMap = (**|11|0|00|1xxxxxxxxxx|<1>[2-9]xxxxxxxxxS0|*21|*50xxxx|*51xxxx|*52xxxx|*53xxxx|*54|*6|*6xx.|*77|*2xx.|*73|*74[0-1][0-9]*xxxxxxxxxx|*75[0-1][0-9]|*8|90xxxx|*93|*96|011xx.|xx.|(Mipd)|[^*#]@@.)
Under ITSP Profile x SIP:
ProxyServer = sip.phonepower.com
ProxyServerPort = 0
RegistrarServer = sip.phonepower.com
RegistrarServerPort = 12060
UserAgentDomain = sip.phonepower.com
OutboundProxy = sip.phonepower.com
OutboundProxyPort = 0
RegistrationPeriod = 3600
X_RegistrationMargin = 0.1
In the Voice Services section:
Under SPx Service:
Enable = checked
X_AcceptSipFromRegistrarOnly = checked
X_NoRegNoCall = checked
X_KeepAliveEnable = checked
X_KeepAliveExpires = 30
X_KeepAliveServer = sip.phonepower.com
DirectoryNumber = (your phone number)
AuthUserName = (your phone number)
AuthPassword = (your sip password)
So, now that the ASP method is gone, I was selecting the list of service providers and selecting phone power. The tech told me not to do that. Essentially you can select generic service provider, fill in a few items from this list, but then go into expert mode and fill in the rest of the items. Not easy!!
But at least there is a way forward.
Also the tech said SPs still in ASP registered mode will eventually stop working
I did not ask about the concurrent calls issue, since we will be going from 4 to 2, but I will - eventually.. unless someone beats me to it.