Special:PageAssessments seems to just timeout when loading on English Wikipedia, leaving a blank page. It loads fine on English Wikivoyage and elsewhere. The problem is probably that the default query is to load all assessments sorted by project (which is too expensive on English Wikipedia).

Possible solutions include not having any sorting in the default query or making the page not run any query by default, which might require overriding one or more of the parent methods from the QueryPage class.