Howdy Daan, sorry to hear of your issues.
The P1A15 error is a Motor Control Unit (MCU) code concerning the rise time or voltage level of the big black capacitor in the MCU. It does not prevent the 3 main pack contactors from clacking and making their noise.
The On Board Charger (OBC) is only activated during plug-in for charging, and it too must have the 3 pack contactors engaged and clacking.
Since you hear none of the usual starting or charging sounds, then i'm guessing that you have some other issue.
Did you happen to test the 12V battery under load. If it is old or weak or worn out, then it could be the culprit even though it may seem to be reading a "normal" Open Circuit Voltage. Take it out of the car and charge it on the bench, then test it with a big load current.
Reading the DTCs is an easy DIY, there are several options for either wired or wireless, and there is a thread here about those options. Wireless uses your phone, android or apple, with either BlueTeeth or WiFi. The wired version iCarSoft i909.
There are some other forums over there in your continental area, uk or eu, that might lend some assistance.