Your stake is inactive because the Validators have reached the maximum amount of nominators allowed. Validators can only payout 256 nominators per era. If a validator has more than 256 nominators, it is considered "oversubscribed", and therefore, only the top 256 staked nominators (ranked by the quantity staked) are paid rewards. In other words, if a validator is oversubscribed and you are stake number 257 or higher, you will not receive any staking rewards. The Polkadot team is working on this limitation. The only solution that we can recommend is to select a different validator who is not oversubscribed