Hi bro,
If u paid the amount after 3 or 6 months or even 1 year, the card inserted into the box will not expire.
You can go to the airtel thanks app and go for dth section and click on help and support and type channel not able to watch and all the steps have went through then the server will refresh/restart the connection.
Or else if u have service engineer number or registered for it, then u can ask him through mobile and say the error code, then he'll ask his own team to refresh the connection. [There won't be any cost by doing this, unless the engineer visits ur site then he'll ask for the service charge even if there's any small work or no work.
Thanks.