I used my Anova for the first time yesterday.
I cooked a nice Ribeye, about 1.5" - 2.0" thick.
I set the ANOVA to 129.5, cooked the steak for 45 min and it came out WELL DONE.
It should have been medium rare at most.
What happened?

Did you finish/sear it off? How did you determine that it was well done: the internal temperature, or just the color?

Yes, i seared it quickly in oil and butter. I determined well by the color.

Doneness is determined by temperature, not color. You say “quickly”, but that’s doesn’t tell us much. Did you dry it off first? How long did you cook sear it (an actual or estimation of time)? How hot was your pan? Did you check the internal temperature of the meat after all was said and done?

They say that it’ll look grey for a little bit after you pull it out of the bag as it has had no oxygen. Supposedly If you let it rest, color should return.

Take your container, fill with water, and put that Anova in set at 129.5 degrees just like you did for your steak. When the water has come up to temp check it with a thermometer that you are sure is accurate. It you confirm the temp is 129.5 (or thereabouts!) then your Anova is working fine and you can proceed on to investigate other possibilities.
Best of luck!