The most immediate way to check is by using the LinkedIn search bar.
The Result: If their profile does not appear in the search results—even when you scroll through all results—and you are certain you were connected before, this is the strongest indicator you have been blocked.
Note: If the person simply removed you as a connection (unfriended you), their profile will still appear in search results, usually with a "Connect" button instead of "Message." If they are absent entirely, it is likely a block.
This report explains the signs that indicate you may have been blocked by another LinkedIn user, steps to verify blocking, limitations of detection, and recommended actions if blocked.
According to LinkedIn’s official policy, when someone blocks you:
Test with a mutual friend (the best method):
Ask a person connected to both of you to check the suspect’s profile.