Hello and welcome. It’s nice that you are reaching out, trying to better connect with your grandson.
In addition to the good advice above, I want to share a few ideas.
Hugs can be overwhelming. Even when they are nice, for me, they just overload my senses and my anxiety. Hugs are not a good way for me to show and receive affection. As a seven-year-old, it is important for children to feel a loving hug, so it’s good that you try to hug for as long as he can tolerate.
Please have faith that even if your grandson does not express himself with language that he can still take in a lot from hearing you speak to him. The things that you say, the way that you say them, and your willingness to connect and communicate is so important and I am sure it is being received, even if that is not always evident.
As much as you can, I would say to focus on activities. Find things that your grandson enjoys doing physically. Whatever both of you can tolerate in terms of playing games, going interesting places together, creating or building things, or possibly something like art or music.
For me, and several others that I’ve spoken to here, there is great value put on simply being together with another person without much pressure to interact in a specific way. Sitting quietly with someone that I trust is the best thing in the world.
Your presence is important to your grandson. Even if he is not looking at you, seems disinterested, or is not giving usual signals of connection, that does not mean your presence is not noticeable and important.