There are often tech problems with eBay on very busy periods, and they don't get much busier then Easter Saturday.
As the function worked okay with Chrome I take it you's solved your problem.
PLEASE remember that there is no buyer protection for motor vehicles bought on eBay, however you pay. Any seller who claims otherwise is telling porky pies. There are so many scams in eBay motors. These range from private sellers not mentioning problems to - according to one senior police officer - organised crime having opened multiple hundreds of fake accounts on eBay for motor vehicle frauds.