"The site collection containing this sandboxed solution has exceeded its daily resource usage quota."
While working with Sandboxed Solutions on Office 365, you might get this error when you try to activate your solution. I faced this error on the Small business version of Office 365 but it has been know to occur on the Enterprise version too.
There is a limited resource usage quota alloted to each SharePoint Online sitecollection. When this usage quota is exceeded (when you try to activate your solution) , this error occurs.
So far, I have found how to resolve this issue on the Enterprise Version of Office 365 only. I am afraid there is no setting on the Small Business Version (The P1 plan) to manage the allocated resources.
The solution for this issue (on the Enterprise Version) is pretty straightforward:
SharePoint Online ->
Select your Sitecollection ->
Select Resource Usage Quota -> (on the top of the page)
Enter the new value in MB of your Usage Quota in the resources textbox->
Done. That's all there is to it :)
Enjoy Office 365!