Since with some updates the gets updated as well, you’ll need to accept it as safe again.
When typing in the error code, please note that the error code starts with the digit 0 and not with the letter O.
When Outlook worked before and you’re suddenly presented with send/receive errors, it is still good practice to verify your account settings and make sure that they are current.
For example, several ISPs have increased their email security settings which could require you to enable SSL or make port changes.
A stuck message is also often a source of having send/receive issues.
While it is easy enough to spot a message stuck in your Outbox, in some cases the stuck message can be a Read Receipt which are hidden messages and thus much harder to recognize as the issues and to delete.