Vpn client on mikrotick, slow connection, what's the problem?

Question

VPN

Good afternoon!
There is a problem, there is a mikrotick RB951N router on it, a vpn client is connected to our server, packet routing rules are configured, everything worked fine for 3 years, and now when connected to vpn, the speed drops to zero!
It is either not comfortable at all or it is not possible to work, the pages do not load! help to understand the problem, where to dig to understand what the problem is? provider freezes!

Answer 1

ipsec?gre?pptp?l2vpn?l3vpn?openvpn? does it work over tcp or udp? mikrotik doesn't understand with udp vpn.