Unable to share Whiteboard outside someone else's organization

I am a member of a company (which I will call "Company A") and months ago shared a whiteboard with several Zoom users outside my company, including someone in what I'll call "Company B." Now for some reason it appears that my ability to share new whiteboards is restricted to people within Company B. 

When I click Share, under General Access my options are "Restricted" and "Anyone at Company B." The option for "Anyone with the link" is greyed out because "your admin has disabled external link sharing." My admin at Company A has not disabled external link sharing and is also affected by this problem. It appears whatever Company B's restrictions are have transferred to our accounts as though we are employees at Company B. When I try to add new email addresses it says "Company B has disabled collaboration with users outside your organization." 

Again, this is happening on whiteboards that are completely new and have never even been shared with anyone at Company B. It's just me at Company A making a new whiteboard, and then it's says I can't share it with anyone not at Company B. 

Tried reinstalling Zoom to no avail.