Getting through Routers - No Audio

[DCairns]

Hi. I am in a Band of 6 folks, based in Scotland, who have been using JamKazam for about 4 months with reasonable success, including doing gigs online. 
Recently there have been a number of software updates, some of which have caused ripples.
Our latest challenge however, is that one of our members has relocated to her flat, which has a new router, and while she can connect to one other player, audio is dropped to all others , with 'packet receiving error' messages displayed. What to do given an error message which gives no forward direction?
There has been a lot of discussion across the forums of configuration approaches.  JK obviously supports a number of routes. Legacy information from videos and the forums does not necessarily hold true now.

There may be a Firewall to block port access in the router, or within the PC/Mac, (or both or neither) with specific application permissions or blanket policies.

It would help if someone could describe what JK needs, in one place, for lightly technical folks! Do the following statements hold true?

Router setup can use any of:

• UPNP - this seems the default, as most PCs and routers in our group have not gone anywhere near port forwarding.
  
• port forwarding - UDP works best, in a range of about 10 ports from , for example 12000.  
  
• Single port NAT ?
  

How can the correct settings on the router be verified?   e.g YouGetSignal.com/tools/open-ports/
Are both ipv4 and ipv6 valid options?  ( I resolved one problem by ticking ipv6 on what I thought was an ipv4 link, - it kept going when unticked ) 
All users MUST use the same ipv4 or ipv6 addressing scheme.

If there is any issue reported by JK, then the cleanest way to reset is to 'restart the client' which is an option on the Manage menu.

Some documentation of the Audio Booster page would probably help too.

When it works, JamKazam is excellent!

Some more description of the actual problem, where any help would be appreciated ! It is hard to tell if this is a router problem or a JK bug.

We have a group of 3 PCs (P1-3) and 2 Macs (M1,2). M1 has just relocated behind a new router.
Various test sessions:
P1, M1
P1 can hear M1 but M1 can't hear P1. P1<=M1.  RECEIVING PROBLEM: The JamKazam client is not receiving audio packets from some session peers. Message.
P1:Untick ipv6, then retick.  All sound established correctly P1<=>M1

P1, M1, M2
P1<=>M2, M1<=>M2, P1<=M1.  RECEIVING PROBLEM P1:Untick ipv6, then retick.  All sound established correctly P1<=>M1

P1,P2, M1
P1<=>P2
P1<=M1.  RECEIVING PROBLEM P1:Untick ipv6, then retick.  All sound established correctly P1<=>M1
P2<=M2.  RECEIVING PROBLEM P2:Untick ipv6, then retick.  All sound established correctly P2<=>M1

P1, P3, M1, M2
P1<=>P3, P1<=>M2, P3<=>M2
P1<=M1.  RECEIVING PROBLEM P1:Untick ipv6, then retick.  All sound established correctly P1<=>M1
P3 = M1. RECEIVING PROBLEM P1:Untick ipv6, then retick.  No benefit. No connection

P3, M1
P3 = M1. RECEIVING PROBLEM P1:Untick ipv6, then retick.  No benefit. No connection

Applying router forwarding rules at M1 makes no difference.

Relocation of M1 was coincident with last software upgrade. PCs on 1.0.3794 Macs on 1.0.3702

Any help appreciated !