FWB help

I have a fwb who I met online, he told me he was looking to be casual that would develop into a relationship, we had been hooking up and hang out and cuddle afterwards for a few weeks. He But last Monday I sent him a text he replied and when replied back, he didn't; about a couple of days later I see that he was online and I was thinking "soo you can be on this app but can't send me a text back". (Ps when we first started talking we would text each other a couple of times a week) What should I do? I should move on, right?