I had over a dozen encounters built and saved in the Encounter Builder, and as of last Friday every single one of them was wiped out. A number of these contained unique content for my PCs and about items/treasure that I now no longer have access to or information on. Is this a system-wide issue or isolated? Can something be done to recover this?  I'm sincerely irritated about this "glitch" and the continued "nat 1" that keeps being rolled by D&D Beyond when it comes to this issue.

Have you tried refreshing the Encounters page? I have been having issues with spells in the character builder an am wondering if it is related.

LOL  Yes, that was the very first thing I did, assuming it was just an issue loading the information. However, it's been a week now and still nothing, so it's definitely an issue where the information has been lost

It might be a caching issue with the server. Have you tried logging out, logging back in, and waiting 20 minutes? That will force the server to clear its cache, which might solve the problem.

Good luck. I have been waiting for customer service for a month now.

This has been resolved.  Thank you to Customer Service and the Support team for your assistance