I have noticed if you play with latest open.mp launcher, there is a problem with function DisableInteriorEnterExits.
Example if you play in a server where DisableInteriorEnterExits are disabled and you switch to a server where Enter/Exit entrances are allowed, you see them disabled... You can not enter even they are enabled by default from the server.
You need to leave the server and re-connect by normal standart way to fix it.