Hi Tom 

Thanks for reaching out in the Lucidchart Community! Based on the behavior you described I suspect that you might have created those documents in a different Lucid account. This would explain why you are prompted to request access when trying to open those documents with the URLs. Would you mind double-checking that you are in the correct account? I would recommend checking any and all Lucid accounts that might be under your email addresses. 

If you're still unable to find your documents in other Lucid accounts you may have under different email addresses we would be happy to try locating them for you using the URLs. In this case for privacy and security reasons we will first need to move your request to a support ticket for one-on-one troubleshooting. Would you mind filling out this form to submit a ticket making sure to add the URLs to the documents you are looking for?