When I have too many apps open and I try to open a new one, I can't connect to Internet

[AC Question]

When I have too many apps open and I try to open a new one, I can't connect to Internet

Why this happen?

 

[ManiacJoe]

Your phone has limited memory and other resources.
Trying to open too many apps causes the OS to close down "unused" apps.
Seems odd that any service related to internet communication would be closed.

Which phone?
Which version of android?
Which carrier?

Do you have any firewall apps running?