Please check this issue and eventually update this part of YAML. Then please find an AppVeyor project webhook in GitHub project settings, find tag-related delivery in the "recent deliveries" and re-deliver it. Let us know if this helps.
Regarding Fallback clouds stack is too big, we are looking into this issue right now. Please use RE-RUN INCOMPLETE button to re-run failed jobs for that specific build for commit 5512ec3d9e43921a60d759a79da71caf6fd4e8da.
Sorry for the trouble. Please let us know how it goes.