I have the same problem with SiteKit 1.2.0 using (Internet Explorer) browser I see the following error on the Sitekit Dashboard and Adsense Tabs:
Object doesn’t support property or method ‘formatToParts’
in t in u in t in Unknown in WithFilters(t) in t in t in div in div in div in div in t in
while Search Console, Analytics and Settings Tabs are accessible.
On (Chrome) browser all the Sitekit Tabs are BLANK, nothing shows
On (Firefox) browser all the Tabs are visible and working
I hope this helps…
