Check the following:
Its exchange account type. Situations like this one can happen with Spot trading. If the market does not offer a good entry point, the trader might prefer to wait for a while and resume trading activities when the market changes.
Its history. If the strategy doesn't trade for more than a month, there may be a problem with the trader's account or they may have decided to pause trading for a while. Monitor the history of the strategy and subscribe only when the trader starts trading again.
All the inactive will be hidden from the list after 30 days of inactivity.