Advisor not responding to emails, conference fee deadline approaching TL;DR:: My advisor, who is in charge of paying a conference paper registration fee, is nonresponsive and the deadline is approaching. What can I do?
I am working part-time in a research institute, which is running mostly from home-office right now.
Together with a professor and my institute supervisor we wrote a conference paper that was accepted in peer review, and the next deadline for the final submission is drawing close.
My advisor is the one responsible for the funding, and I talked to him (voice chat) about paying the registration fee. Afterwards, I have emailed him about other issues as well, for example me needing to get permission to enter the institute for paper-related things (need to update a plot etc.). I have not heard from him since around 3 weeks. He may very well be on vacation, but has not set up an away-message. He may or may not have forgotten about the deadline.
Question: How can I handle the registration fee deadline, without knowing whether my advisor will take care of it in time?
I see some options here:

Wait and do nothing about it, the problem might resolve itself
Escalate the problem and email either the professor, a higher-up or a different institute advisor who may know which steps to take
Pay the fee myself and hope it will be covered by the institute later

Note that in theory I could afford to temporarily cover the fee, but generally I would like to avoid it.

This question may very well be overly cautious but raising money from the institute may take some time.
I am aware of this related question about withdrawal due to funding, but I do not want to withdraw the paper.
Many conference organizers are well aware of how &quot;organized&quot; some advisors / faculty / university accounting departments are.
Contact them and if you can provide evidence that it will &quot;eventually&quot; be paid then they will usually accept that.