SIP 200OK over wss not recivied to asterisk

asterisk version: 13.21

using VPN, local and remove both candidate type is the host.

Asterisk sends invite over WebSocket to SIPJs client
SIPJS client response with trying, ringing and 200 ok
SIP JS client retransmit again and again 200 OK as ack not received from call server.

As checked the asterisk sip logs: 200 ok doest received hence asterisk does not sends ack.
any idea why 200 OK not received at asterisk?

What channel driver is in use? Did the Websocket connection drop? Does it not show in the SIP trace in Asterisk?

channel driver : chan_sip
browser : chrome 80
Websocket connection does not drop.
no it does not show in SIP trace in asterisk.