You do not say how long ago your daughter married or when she had her child.
It strikes me she has been putting a lot of time and energy into making a good relationship to her in-laws and has simply taken your love for granted while she was doing so.
We all know the in-law relationship can be difficult. Do you know if she has been having trouble with them?
Wait til restrictions are lifted then invite them for lunch or something similar, preferably son-in-law as well.
If your daughter says they are busy, say you appreciate that, and you are too, but you have missed her (them) dreadfully, so you hope you can find a convenient time.
If that does not work, you will need to ask straight out whether you have said or done anything that has hurt her.
If she says, "No, of course not." there isn't much more you can do, unless you can say jokingly, " I suppose, I am just jealous of your mother-in-law, she seems to see you more than I do." However, that is the kind of remark that could back-fire, so perhaps you shouldn't risk it.