Issue:
I lost power for a few days. I lost internet connection for a few days. Power was restored, and then later the internet. When internet was restored, my dockers using Linuxserver.io Tailscale docker modifications did not reconnect with Tailscale. The Tailscale administration app showed the dockers offline. The dockers were not pingable from the Tailscale administration app.
I suspect the docker containers communicate with Tailscale upon startup. If the docker container doesn't reach Tailscale at startup, it won't retry connecting, and there will never be a connection with Tailscale.
Workaround:
Restarting the docker containers resolved the issue, and the docker containers connected with Tailscale.