3CX SMB/Free Incoming call issue

[FLCC]

Since yesterday morning one of our instances (3cx smb) has been able to call internal and outgoing fine but as soon as anyone calls them it will either ring once or four times, then report busy here (on the callers system).
The routing goes direct to a digital receptionist which never engages.
3cx logs show no activity for the incoming call.

 

[KyriacosS_3CX]

Hello,

Have you contacted your SIP Trunk provider?

 

[FLCC]

they replied with this
You might need to run a PCAP trace on the 3CX to see if the INVITE’s are hitting the system.
It looks like your PBX is not responding to our invite at all, please can you whitelist the below Ip's and ranges and retest.
93.95.124.0 /24
Ports:
5060 – UDP/TCP
10000 - 60000 - UDP

I dont beleive any of that is possible on 3cx free?