Please follow the below template, it will help us to help you!
Please ensure that you are running the latest version of the beta code. Run pihole -up to update to the latest, then verify that the problem still exists before reporting it.
[done]
Problem with Beta 5.0:
"Unable to complete update, please contact Pi-hole support."
*** [ DIAGNOSING ]: FTL version
[✓] FTL: v4.3.1 (https://discourse.pi-hole.net/t/how-do-i-update-pi-hole/249)
You are also running an unsupported OS (Stretch and Buster are currently supported, Jessie is EOL and not supported). This may be contributing to the problem.
Uhhhh. OK. Had no idea I needed to go find a different OS and start all over.
That takes me completely by surprise.
That puts a different light on things.
I very much appreciate your response. I'll try to figure something out.
Understood. No doubt you are right -- and I appreciate you looking at this.
No way I could/would have known. I assumed (clearly wrongly) that a periodic OS update would be sufficient. I have one operating 800 miles away. It'll be a long drive ... ;<(
Btw you don't need to find a new OS but can either reflash the current version of Raspbian (Buster, that's two major versions never) or upgrade the distribution by changing the apt list suite. I would recommend a fresh flash but the following might work fine as well, depending a bid on amount and type of packages you've installed:
sed -i 's/jessie/buster/' /etc/apt/sources.list{,.d/*.list}
apt update
apt upgrade
apt full-upgrade