Android phone not seeing box files in the past two weeks.

I have several excel files that I update on a regular basis. In the past, there was no problem opening the file on my laptop, ipad or android phone. I have the excel app on my phone...I would open excel and then click on the file (I pin the most used at the top). Underneath the file name, it used to show the source of the file as 'box'. 

Just in the past couple of weeks, it now says 'other cloud storage' under the file name and when I go to open it, I get the following error message:

"Office can't find. It may have been moved, renamed, or deleted". The files are there, as I can access from my ipad and laptop, but suddenly, my phone can't find them. If I go from the box app on my phone, I can see the files. 

If I am in excel and I click on the open file icon, it used to show me Box as an option, it is no longer showing. If I click on 'add a place - connect to cloud storage', it doesn't list Box as an option...it lists 'One Drive', 'Dropbox', 'Sharepoint' and a bunch of others I have never heard of, but not giving me the option to add Box.

Please help. I have been a Box customer for a long time and would rather not have to use One Drive or Dropbox as my default file storage between devises. I don't know what has happened in the past two weeks or so to change this it has been working great for years!