I would also like to know the answer to this question.
I followed the link Becky added and changed my Digitmap Timeout to all 15 seconds. My phones still timeout after 3 seconds. I changed it through the web interface. I also downloaded the config file, edited it manually, reuploaded it. They still time out after 3 seconds. This setting does not change anything."Digitmap Impossible Match" also does nothing.
@Andy Cunningham might be because your phone is set up via assisted provisioning - so whatever you configure gets overwritten by the config on the provisioning server.
If this is correct you have 2 options.
1. Remove the provisioning string pp.ringcentral.com/pp from the phone and then provision the phone manually with SIP credentials.
2. Stick with assisted provisioning and get RingCentral to do a custom config for your phone, which will overwrite the default config on their provisioning server.