Being able to view the conversation and send messages to another user doesn’t mean they haven’t blocked you.
Just because you don’t see someone’s online status doesn’t mean they’ve blocked you—remember, WhatsApp keeps the signs of blocking pretty ambiguous to protect user privacy.
If you have a mutual friend in common with this person, you could ask them whether they can see this person’s Last Seen status (if you feel comfortable doing so). If the mutual friend can confirm that this user hasn’t turned off the Last Seen feature, you’ve likely been blocked.
