Your feedback profile shows you have received and given 8/9 feedbacks for purchases this month alone.
Have you perhaps received 2 unpaid item strikes in the last 12 months? This will prevvent you buying from the majority of sellers.
If, not just sent the seller a message to see if they have any blocks in place preventing you from buying.
We have no direct access to your account so can only guess at the reasons, you could contact eBay Csutomer Services they have that access and can perhaps see if there is anything showing, perhaps an out of date payment card, etc .
To Contact Customer Services it's a Live Chat, or you can select to speak and request a Call Back. Click on this link:
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
On the left sidebar you can see Have us Call you or Chat with Our Automated Assistant.
On weekdays lines open between 8 a.m. and 10 .m.
On weekends they open between 9 a.m. and 6 p.m.
