Problem (maybe?) Solved....

UT's Box expert following suggestions (pictures are hyperlinked):

Sign into your Box account and ...
Click the gear icon in the upper-right corner and select Account Settings
Select the Apps tab
Under Applications Linked by Single Sign On, click reset account association (next to Google Docs)
The next time you try to edit something using Google Docs, Box will prompt you for permission to do so (you may need to sign into your Google account as well). Allow access.

This is not a one time fixes all cure. The google reset account approach may need to be reset multiple times.

If after doing this, Box still isn't opening the attendance document with google docs there are other options:

download the document, edit, upload (sigh, so early 2000s)
email plus@austin.utexas.edu (formally Leta, still welcome to email me in addition to PLUS address) the names/eids in excel and in the body list the day/time/class of study group. Be sure to identify what class and professor you're reporting out on. (Please also include any information on when document was not opening–using a mac/pc, firefox/safari/internet explorer, etc)
edit with box (requires a download, does not have good interface with google docs). This will create the option of editing in Microsoft excel--right click, edit with Microsoft excel. Alternatively seek the triangle to the right, edit with Microsoft excel (note: user must hit save for this function. I do think this works more consistently but does NOT save changes if multiple folks are trying to open it simultaneously, and if someone locks it for editing—to prevent multiple folks from opening it simultaneously- the have to be sure to UNLOCK it after they have saved it).

The concerns these (except email) is that one user may trump another, leading to unsaved edits.

Have you brainstormed another good option? I want to hear it!

Attendance is the only quantitative data we collect; it is super important it gets recorded.

Thank you for your diligence!