When someone stops replying, switch channels, gently name it, or let it ebb, and keep showing up with zero expectation either way.
I get this question about twice a week in coaching: "What if they haven't answered my last few messages?" The first thought is always "yep, they hate me." That's your ego overstating a tiny social slight. Focus on your second thought, the more logical one. Maybe they're slammed. Maybe email is the wrong way to reach them. Maybe they keep meaning to reply and feel bad it's been so long. You can't control their timeline. You can control whether you're still there when they surface.
Pick one of three moves:
Whichever you pick, keep the low-stakes signals going: a birthday note, an article they'd like, a quick "thought of you." No ask. No agenda.
A friend of mine went fully dark for three years. I kept sending my quarterly update, a birthday note every year and the odd "thinking of you." When he finally reached out, it turned out he'd been going through a lot and froze every time he went to reply. He also came back with a business opportunity.
"Been trying to reach you a couple of times - I take it you're slammed. Here for you whenever!"