What is the reason why I cannot make a stake now for over a month? I don't think it's my balance, as it's high enough. Is there something on the wallet I might have turned off by accident? I've staked the coin now for about 3 years.
Maybe your internet drops out just before you are supposed to get stake, so it starts from 0...
If you don't fear putting trust in 3rd party,
https://btcpop.co/Staking has worked great for me.