Not only Arthur, Raffaello and Bandit's heart of affinity, but Liam's doesn't show up either.
Viewing post in Bug report
Liam was showing just fine for me, if it really is a matter of refreshing the gauge by buying something or battling them, Liam's probably the easiest since his beer are available for free, it's harder for character that sell their goods only once and after that you can't buy anything from them if you already bought everything