There are a couple of things to check and errors you can get. A solid amber or yellow only light according to the manual for that unit (had to google and download it, does not come with the charger) states the fault is "Restart after interruption of charging" and the corrective action is "Wait two to three minutes until there has been a restart. If charging does not start, disconnect the charging plug from the vehicle and plug it back in. If the error occurs consistently, have the charging cable checked by a qualified service technician. Volkswagen Group of America recommends a Volkswagen partner."
I have seen a solid yellow light come on a couple of times following a power failure. Turning the breaker off and on (or unplugging it) seemed to take care of it. I will post the complete troubleshooting table below.
I started noticing our overnight charging was taking longer and longer and then discovered after about 10-15 minutes of starting a charge, the indicator on the unit was yellow and blue. Manual indicates the means the unit overheated but was continuing to charge at reduced power. And it did, it reduced power from 7+ kw to 5.5 kw and sometimes lower. Turning if off, letting it cool down, then recharging only at night seemed to help for awhile but then it started doing this every charge. Further the charger was not unusually warm either, if anything felt a little cooler. The unit, which I bought with the car last September was clearly failing. To make sure it was not the car I took it to town and plugged it into a Destination charger with an adapter, and got a steady 9 kw for 15 minutes and concluded this was not the car, it was the charger. Also had no trouble with DC fast charging.
Aside from unplugging the charger or resetting the breaker, I have read other people have found fault with the removeable connections to the charger being ever so slightly loose (to correct, take off, then firmly reinsert) or sometimes a fault with the 240 volt outlet its plugged into. (to check plug the charger into a different one somewhere else if you can).
Since mine had less than a year on it, I took it back to the dealer (100 mile round trip) and got the old runaround. Parts would not exchange it because I bought it with the car and not as a standalone part. Service would not exchange it unless they could take the car in and check everything out and that was expected to take all day and would have to be done next week. (and I just had the 30K service done less than 3 weeks ago). So I decided to get another charger, pay for it, and get this problem off my plate. The new unit has no trouble charging at all.
[Despite the early failure, I like the VW charger's simplicity, portability, level one charging plug if needed. I can do things where the charger is at to try to keep it cooler and put a load on it only at night. There are other higher output, cheaper chargers on Amazon, but my take on the reviews of those is that while many are happy, for a significant percentage of buyers, they get really hot and some reported melted charge ports on their cars].
I might go back to the dealer and let them check things out and maybe I will get a new spare charger out of it, who knows