I was running into this because I was using mxpv/podsync docker image (2 years out of date) instead of the ghcr.io/mxpv/podsync image. Once I switched the issue was gone. The README.md needs to be updated

See my PR here #657

Podsync uses yt-dlp to download from youtube. Last time, Youtube changes their policy, and now yt-dlp have problems with downloading. More about that yt-dlp/yt-dlp#10128

on docker: docker exec -it podsync yt-dlp -U
This updates yt-dlp for your current instance only!

docker exec -it podsync yt-dlp -U

I did this but I'm still getting download errors, and asked to sign in to confirm that I'm not a bot

on docker: docker exec -it podsync yt-dlp -U This updates yt-dlp for your current instance only!

I had to run docker exec -it podsync /usr/bin/youtube-dl -U instead, and it works now.

I put together a docker-compose that includes the update step if anyone finds it helpful:

services:
 podsync:
 container_name: podsync
 image: ghcr.io/mxpv/podsync:latest
 restart: unless-stopped
 ports:
 - 80:80
 volumes:
 - ./data:/data
 - ./config.toml:/app/config.toml
 entrypoint: /bin/sh
 command: -c "youtube-dl -U || echo 'Update failed, continuing...'; exec /app/podsync --config /app/config.toml"

Edit: This might actually be redundant if you enable yt-dlp self-updating in the config file.