Astrill service in the router will last around a year since you bought it, when the Astrill account is out of date, you Astrill router will not work either.
Here is how to renew the account in the router.
1. You need to login to the site members.astrill.com, check your account info, when you renew it, make sure you need to choose the
ProAdd on (very important for using in the router in China, as it provide you 2-layer protection)
Home Plan (if you need to use the Astrill on your phone or computer when you are not in the house)
2. After the account renewal is done, you need to unplug the router of the TEK VPN router, and plug it back in.
Wait for 5 mins, then go back the Route page > Astrill VPN page
You should be able to see the new expire date of your Astrill account.