Have you tried the usual browser trouble-shooting steps (clearing cache/cookies, restarting browser, trying a different browser and/or mobile data)?

Also, could you check your item history to see if it has taken the Pieces of Cloud, and also if it has taken aging points for the 'looped' agings?

Does the horse's age increase with each aging, or is that stuck when you age?

I've been on different devices, and it's showing the same thing

Ageing points have been 'earned' from the PoCs (came up in the notifications), the last ageing was overnight (so no APs used), but you can see in the horse's history that it's got water, carrots, feed etc before and after the PoC. The age does increase.

Will see what happens after another ageing and will send a ticket in if it's not fixed

Just aged again, age in months goes up, horse is restored to 94% health etc just like for a new day, but the history gives the previous day's history without having done anything (no PoC notification this time though, or history from two ageing prior)

Does it let you do any of the care actions, even if it's in the history of the previous day? (for instance, if you had given the horse a drink yesterday, is the care action greyed-out or are you able to still do the actions on a new day?)

It's normal that you can see the old history. It shows all the actions which were done on that date at least twice (old + new). If you go back with pocs and hit that day again, doing new actions will be simply listed on the history log on top. So you can see twice drinking, twice food or whatever you did.

However you should be able to collect passes again. Did you deage it and age then to a day where you know it gave passes before? If it gave passes on 5th birthday and you give the poc when it's 5 years and 10 months, then you won't get passes again because the pass collect day would be 5 years and you would only reach 5 years and 6 months.

I know it's normal the first time, but didn't think it was usual to happen for the next 4 ageings in a row.

@Anarky, I am able to do all the care actions again after ageing

@Eleyii no, I put 2 PoC on to get the horse to 2 months before the 'obtain passes' age