So, if I understand your question correctly, you are asking if story points are still meaningful if only a few developers (not all) estimate those story points for the work that you need to do in the sprint?
Planning poker is a consensus based technique for estimating. The idea is that when all the people doing the work discuss and estimate a task, the estimation you get is better than if only one developer (or fewer) did the estimate. More heads are better than one basically, because a developer can overlook something that another developer can catch and raise attention to. So, when a few developers estimate, that estimate can be less valuable than the estimate given by all the developers.
I say "can", not necessarily that it "will". It really depends on how much experience each team member has, how much practice they have with estimating as a team, who are the actual developers missing from the meeting, how many times the people disagreed on things before, the difficuly of the task, if the task is something new or something similar to what was done before, etc.
But I think you are trying to solve the problem in the wrong way. The problem here is not the meaning of the story points, but the fact that not all developers are at the planning meeting. That is what you need to fix. I understand that some people are not in the office because of the COVID situation, but they can join remotely. If they can work remotely, it makes sense they can also join a meeting remotely. Find out why they aren't joining the planning and try to fix it.