Signs that you might be blocked on וואצאפ include:
1. You can no longer see a contact's last seen or online status in the chat window.
2. You do not see updates to a contact's profile photo.
3. Any messages sent to a contact who has blocked you will always show one check mark, and never show a second check mark.
4. Any calls you attempt to place will not go through.
However, these signs can also happen if the user has simply changed their privacy settings, so they're not definitive proof of being blocked.
Unfortunately, if a contact has blocked you, the decision to unblock you is entirely up to them. You cannot unblock yourself. The only way to get unblocked is for them to unblock you from their end. You may need to reach out to them through other means to request to be unblocked.