looks like you have covered all the standard bases. I think it's time to cut your losses, bit the bullet and "reset to factory defaults" as you could spend more time trying a bunch of things with potentially no positive results and still have to do a full restore. I say do that and get it out of the way and if need be, work backwards again from a clean install of everything.
by the way, I've gotten that "try again" message from Netflix on my Roku Tv's and once in a while from my ATV4K, but, simply saying ok and trying to start the episode/movie again, it worked out fine. it sounds like what your saying is, Netflix no longer works for anything no matter what.
best of luck, keep us posted.
TCL-65R615, 55P605 DV/HDR10 & 49S405 HDR10, Philips BDP7501, BPD7502 UHD Players
Oppo BDP-105D, 105, 93, Marantz AV7702MKII, NR1607. Xbox One S
Emotiva XPA5,UPA2, UPA200 & Mini X Amps, ATV4K 32gb
Speakers, Polk SDA-2, Monitor 10A & 5A, Axiom M80,
VP180, QS8, M2, QS4, ATMOS 7.1.4 & 5.1.2 NYGiants!