How long to get EBay involved?

An item I sold on November 6th I shipped the same day using EIS going to the UK and on the 24th the buyer opened an Item Not Delivered Claim because it was estimated there between 9th-18th. I was confused why they opened it since the tracking was automatically uploaded so they could clearly see it’s just taking longer than expected.

On the 24th I messaged them on the claim and said looking at the tracking it left the states over the weekend and then on the 26th I told them I see it arrived with Royal Mail and just sent them the RM tracking there too.

When I checked on the 28th I see that they need to pay the import charge and they haven’t yet and I just told them this too today in case they didn’t know. Now I see a fourth step I see I can also take for resolving this is to ask eBay to step in and help, and I’m wondering if I should at this point because my other payments are on hold because of this too and I wasn’t sure if I should maybe wait another day to see if they respond or if they paid the customs charge?