Some co-authors unresponsive when I asked for consent for submission to biorXiv
2 weeks is a fair amount of time, so yes, remind them. You could also write something like "If I don't hear from you by [time] I'll assume you consent to submission", or "I'll submit this by [time], if you have any objections please let me know before then".

That said if you have a PI, you might as well ask them what to do. There's no reason not to, especially for contentious decisions that might lead to bad feelings.