Sourdough

I'm hoping to pick the collective brain troubleshooting my starter, Alfy. I made amazing sourdough bread about two weeks ago now (the first offspring of my new starter), and then I stored Alfy in the refrigerator on a Wednesday. I fed him Saturday and again on Tuesday by removing half of the starter and mixing in equal parts water and flour (50/50 AP and whole wheat). The last time, I took him out of the fridge and left him it at room temp to try and use the next day. But he didn't pass the float test. It's been 5 feedings at 12 hour intervals now and he still won't pass the test.