Logmein Hamachi slow on specific network

I use Hamachi to connect to a site for work. It worked well until a server upgrade last month. 

The site has become slow and is often timing out despite Hamachi connecting and good up/down speed.  

Same computer and app work fine with the site on other internet connections so the problem seems to be isolated to my network or ISP.  Centurylink has upgraded the ont and router in the last week with no result .

Any idea what could be causing the loss in connectivity or how to fix?

Thanks