"406 Not Acceptable" error is while 'Crawl Meta Data' of a website
It can be fixed by changing the user agent.
1) Login as admin to seo panel
2) Go to Admin panel => Reports Manager => Report Settings => User agent:
Change it to => Mozilla/4.0 (Windows; U; MSIE 9.0; WIndows NT 9.0; en-US))
Save and it will fix your issue.