You have already given this person 2 gifts this week, at the start of every week?

[Dunsparce]

Whenever Sunday comes around, all of the gifts for the week are supposed to be reset! I want to be able to reach 8 hearts with Penny, but I can't ever give her a gift! It's like she specifically is locked at 2 gifts forever. Is there any way to fix this? It isnt like this with anyone else! It's been going on the entire Spring season

[Inny【🐭】Nazrin]

Reset day is Monday now.
But you are not the only one having this issue. And I am unable to replicate it to try and find the cause for it. If it's been multiple weeks and it hasn't reset properly, you could attempt to use SMAPI to reset the gift counter. Some people have reported that seems to fix the issue.

[Sweet 'N Low]

I've had the same problem. It seems to happen with some NPCs but not others. I haven't been able to fix it yet (though I haven't played since the newest patch was released), but I've heard that some people have been able to fix it by giving the NPC a gift on their birthday. (I can't confirm or deny that, but I've seen people saying it worked for them.)

[Theblender2000]

Same thing happened to me, but with gus AND demetrius (trying to get to 10 hearts with as many people as possible right now)

[Mondai]

This is, unfortunately, a known problem. At least in the forums here. As Elves said, supposedly this can be fixed by giving a character a present on their birthday... Other people have been able to fix it using a mod, I think the SMAPI cheats menu? But I'm not sure how, since it's not a mod I would ever use. And fortunately for me, I haven't run into this bug yet, so my advice is a bit limited.