Clear the cache of the site and also clear your browser cache.
If you use I.E. clear the cache (Tools, Internet Options, Delete), close ALL open I.E. browser instances, now open I.E, clear the cache again and log back in to the site. See if the issue is resolved.
Also, try a different browsers to see if that solves the issue.
If not, read the upgrade instructions again and see where you went wrong. Or hire someone to upgrade the site for you.
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