Should I attempt to top up using the TNG app or buy new card?

why ask here? you should call celcom..

You can still reload If the Credit validity expiration is no more than 50 days

Isn't it valid 30 days from the topup expiry and 90 days grace period .. It's always recommended to topup at least RM5 to keep it active .. my DiGi is Postpaid and my Hotlink is 365 days activated expiring this year April ..

I always keep referring to Hotlink app for any notification .. If user not keen to keep an eye on that, just leave it terminated and buy a new number

The number should be gone & route to recycle already 😁

U check using celcomlife app better.