Why can't I add more funds to my account using my linked bank account? It says insufficient funds but I have enough in my balance?

Moreta checks your bank balance to ensure you have enough funds to cover:

Since we haven't received the funds from the bank yet, they're still considered in-transit and we cannot see from our side if the funds have left your account. If you want to load more money, add additional balance to your bank account (like Wise) to cover both the new amount you'd like to load and the in-transit amount.