I just had a case opened and had no problem seeing the details. (Which would tend to indicate they should not have been able to open a case in the first place, but that is a whole other issue).
So, it would appear to not be eBay specific. Try clearing cache and cookies, using a different browser, and/or rebooting your computer.
If you are using a phone, try the 'classic' site (full version) or using a computer. Radical, I know.
