I was canning hot packed chicken for 1:15 minutes and the power went off after one hour. I left everything there and I could hear the boiling in the canner for the remainder of the 15 minutes. The power came back on after 25 minutes so I set it for the remaining 15 minutes. Is that ok?
Barring the somewhat unlikely case that the pot was boiling with pressure maintained for 15 minutes with the power off, official advice is that the timer restarts from zero after an interruption (so it should have been processed for an additional 1:15, not 0:15.)
I'll have a look around for some of that official advice to link. I've seen it in print enough to know it.
IMPORTANT: If at any time pressure goes below the recommended amount, bring the canner back to pressure and begin the timing of the process over, from the beginning (using the total original process time). This is important for the safety of the food.
However, this answer suggests an officially sanctioned approach from Germany/Austria (double-processing in boiling water) that might allow recovery rather than discarding the food. https://cooking.stackexchange.com/a/103220/34242 You could, of course, use the pressure canner rather than just boiling water for the second go-round.