Being left out of plans hurts. Tell them once, clearly, before you decide what it means.

Being left out hurts immediately and then starts generating theories. Within a day your mind has supplied a full explanation of what they think of you, and that explanation is usually worse and less accurate than the real reason, which is often thoughtlessness or a group chat you are not in. The hurt is real either way. What is unreliable is the story built on top of it.

You are allowed to ask. Say once, plainly and without accusation, that you noticed and it stung, then listen to what comes back. If it keeps happening after that, you will have much better information about where you stand.