You seem to have two problems
- No DPD collection
- Loss of Prime
1 Seems to be a hot topic of debate which you may or may not resolve.
2 Is another matter that I have not seen covered.
For 2. I would suggest that you change the listings that need DPD to another shipping Template and put in a POA to get Prime back whilst you try and resolve problem 1.
Be aware that Amazon have no interest in excuses, once you see a problem you really need to sort it fast, which would have involved taking action and de listing those items from Prime shipping sooner.