Rinkeby: Transaction was not mined within 50 blocks

Hi, I am on the Ethernaut CoifFlip puzzle. I am connected to the rinkeby testnet with my wallet. Transactions don't go through when on the Ethernaut page (remix works). Example: see tx hash: 0x089ded2477a616f4e681e0406b60e5ade69e7f20b4acb8b95045c60d308d4ab3
Not even "submit instance".
Etherscan shows "This txn hash was found in our secondary node and should be picked up by our indexer in a short while."
Is that an issue with Ethernaut or am I doing something wrong?

Later that day etherscan showed some pending transactions, after solving this I am back to normal and all works as expected.