5.4.6 was previously a leisure release but has since been upgraded to a MANDATORY UPGRADE. Please do so as soon as possible!

Installers at github here:

There was an unintended change in the consensus mechanism that results in 5.4.6.0 wallets having a different message contract version number than 5.4.5.0. A failed transaction at block 3190603 due to the version change resulted in all older 5.4.5 wallets forking from the main chain by rejecting this message while 5.4.6 wallets accepted it. These older wallets MUST upgrade immediately to avoid being left behind!

Wallets on the forked chain will have a low difficulty (<5) and be more blocks ahead. Wallets on the correct chain will have a difficulty of 13 or higher but appear a few blocks behind.

5.4.6 Wallets on the correct chain may show out of sync. This is because the forked chain technically has a higher block count currently as it is slightly faster. Do not worry about being out of sync it should resolve in a few days. If your difficulty is high, you are on the right chain.

Do NOT fresh install your wallet. Simply upgrade and it should reorganize within a few hours.

Discord announcement here