can't open a feed

[isomorphisms]

Clicking on a feed on the LHS.

An internal error occurred during: "". 
java.lang.NullPointerException

Windows 10

[genodeftest]

Please have a look at #7 and #8. RSSOwl is effectively discontinued, so I recommend you don't use it any more.

Anyway, without a log file or at least more infos on the exception (like which class it cannot find), I can't help you at all.