@slamjam I am quite sure that the problem is not on the ER707-M2 if you have not configured other types of VPN on it, I asked you if you have configured SSL VPN on the ER707-M2, you have not answered...

@slamjam You have Fortinet I see, sorry I didn't see that. try with slightly stronger encryption, I have vpn against cisco, unifi, sonicwall and microtik, it works without problems, but I have not...

@slamjam you should not use this encryption, it is outdated and insecure, try this one instead. Do you have SSL on any of the routers? Is there ER707-M2 on both sides of the tunnel?

@slamjam I myself have two ER707-M2 with site to site vpn, there have never been such problems, do you have any screenshots of the vpn configuration? Do you have other VPN services on the router such...

@nicolati I haven't tested with mac autetication but I'm pretty sure there's no difference. Have you turned off random mac address on your phone then? if it is on, you will get a new mac every time...

@Savgar check your network cable, try and connect the access point directly to the router with short patch cables that you know work.