I have an older N79S which used to work fine, but after moving and trying to set it up again, I can't get it going. Here's what I've tried:

1. Putting it on the charger overnight, then trying to run it with the "Auto" button, but it would just leave the charger, then start beeping
2. Resetting the battery by putting it the charger for 3 minutes, taking it off, repeating 2 more times, then charging it again; same result as before
3. Tested the battery with a voltmeter and, since it only showed 14v, I ordered a replacement. After putting in the battery I added the vacuum to the Ecovacs app and it ran for a while, then returned to the base-station, but it keeps backing off, then trying to re-dock, and eventually just stops and the app shows the battery as being dead
4. Did a full reset of the vacuum by holding the "Auto" button for 3 minutes & re-added it to the app, but the same thing still happens
5. Tested the charging station contact points with a voltmeter and it shows 19 or 20v

Overall it seems like the issue now is that it's not charging, and since the charger shows 20v it might be putting out too much power or maybe that's normal. So any suggestions for what to check next, or does any of this sound like it's definitely something? I'm considering buying a replacement charger or motherboard off of ebay, if I can establish what the next likely point of failure is.

Thanks in advance!