My ISP is Vox and they provided a Mikrotik hAP ac lite routerboard

I am able to make calls from the handset but when I try and phone in there are problems.

Either 

1. the call does not connect - i.e. there is just silence from the handset making the call (this is generally the case) , or
   
2. sometimes (but not always) if I am simultaneously logged onto my dashboard the handset making the call will have a ring tone and the call will be shown on the dashboard (see below).  When this happens, occasionally (but not always) there will be a ringing sound.  The handsets do not ring at all