Sorry to reopen a slightly old thread, but I'm having the exact same issue with a Frigidaire ATF6000FS1. Wonder if anyone could provide me with the procedure for running a diagnostic so I can go from there. Although I suspect the door latch might be the issue. I wiggled the door around for a while during the spin cycle and got it to go up to full speed once.
Is it draining all the water out before the spin? Is there water in it now?
If it drains good, then its likely a bad door latch assembly thats causing it not to spin.
Here's the repair manual for your model, put it through a diagnostics(page 62 in the repair manual) to see if an error code comes up:
Affinity Horizontal Axis Front-Load Washer (6000 & 7000 Series) repair manual: www.applianceblog.com/manuals/5995456851_affinity_washer.pdf
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