I would assume perhaps that while you were in charge of the Kidderminster harriers, you were only simulating the matches in your division in full detail. Every other league would not be simmed in full detail and thus you cannot see the replays for these games, and in order to view the goal of the month/season highlight the game in question would need to be replayable/watchable, which it isn't if you haven't been simming these other leagues in full detail. You can check if you have been simming the other leagues in full detail or not by going into your preferences I believe, but I think by default it only sims the league you are in as full detail, and maybe later stages of major tournaments.
Seeing as you just joined Bolton, I imagine if you check your preferences, the league you are in now with Bolton will say its simming in full detail while your previous division with Kidderminster will say it is not in full detail, but that would have just been applied when you switched teams. Give it a full month from start to finish in your new league and you should be able to watch the goal of the month for it, while you'll find that the division Kidderminster is in will no longer be able to watch the goal of the month.