I had someone PM me a few weeks ago & I can’t respond to them as the message won’t go through. Why is that happening?

I also tried to post up a message on the public message section of their profile explaining things but none of my messages are posting there either.

Why’s that? How can I fix that? Does this mean that I might’ve been blocked? I’m confused & upset. I’d appreciate any help. I took a break from this site. Hopefully that person didn’t think that I was ignoring them.