RitcheyC

I know this is way late, but I just encountered this problem and have found a solution that works without having to uninstall any mods and doesn't cause any bugs. Reset AFT by using the Tweak Commands ability and then going to Tools. That's where the Reset AFT option is. Click it and follow through with it! Save when it tells you to at the end! Then you load that final save and wait for three to four days and Serena appears at Fort Dawnguard. Then alls you have to do is pick her up and Summon All Followers to regain your lost buds.