Ah… it seems that your website blocks script execution. Javascript in storeEval is run in the context of the website. We have seen similar reports, for example, with macros on github.com
Workaround: A workaround will be to switch to a different website (e. g. have a9t9.com open in a different tab) while you run storeEval, and then switch back.
Solution: We will soon release an update where a new version of storeEval can run in a sandbox, so websites can no longer disturb or block it.