Who else cant find the forum in the nexus home page?!

After you've signed in, did you expand the Tech Center on the left side, and what is it showing?

Once I logged on from my PC I finally saw what you show here. But still from my mobile browser none of the drop down options show up. I can see the tech center icon but when I click it I see blank spaces where the links should be.

I had the same problem few minutes ago, went in circles, the way I finally got to forums was: after signing in selected PCDMIS from products on Nexus portal home page, at the bottom of the page clicked on "Visit the forum" which took me back to main Nexus sign in page, clicked on the last link on the left side "Visit the Nexus Community" under "To browse the PC-DMIS community Group anonymously" and ended up in forum already signed in.  This way might work for your mobile browser.

I had the same problem few minutes ago, went in circles, the way I finally got to forums was: after signing in selected PCDMIS from products on Nexus portal home page, at the bottom of the page clicked on "Visit the forum" which took me back to main Nexus sign in page, clicked on the last link on the left side "Visit the Nexus Community" under "To browse the PC-DMIS community Group anonymously" and ended up in forum already signed in.  This way might work for your mobile browser.