-I know this may seem basic, but resetting the SPA would be the first thing to do (power off, wait a minute and power back on)
-Ensure that there are no changes
-Preferably make sure you have STUN set up
-Ensure router has UPnP active (or ports open and pointed to SPA)
-Try calling from a different SIP Broker PSTN access number if possible
-Ensure you have not made any changes lately to Symmetric NAT handling (the setting on the VoXalot main page when you log in)
-Enter your VoXalot SIP URI here and see if the ECHO Test call comes in
SIPBroker - EziDial
-Make sure there are no Internet Connection problems (although you mention other providers work). Run a speedtest, or maybe VoIP test at
TestYourVoIP.com