If service stop working what happend?

If service stop working what happend?

Hello,
 I installed ADSelfService Plus to the customer server and starts as service. Some time happned that the web console is down and I´ve looked to the service is not running (is setup for automatic startup). If I start MFA endpoind protection with Google token and the service will be down can users login into the server with username and passowrd without MFA autenthication or they can´t login in to the server?

And if I boot into Safe mode is there the ADselfService Plus working too?

Thanks
Tomas