Thunderbird eliminated most on-line folders and won't let me create new ones to replace them and read email stored in them.

In order to delete a large number of files in an on-line folder (an IMAP folder?), I deleted the folder and then created a new folder with the same name. The next time I opened Thunderbird, all my on-line folders except Sent and Trash were gone, and I could not re-create the folders that were deleted. I cannot access files stored in those folders or move files to folders with the names of the deleted files. I can create files with names not used before. But I cannot create a new Junk folder to hold files that Thunderbird routinely sends to Junk. I am not getting some emails in the process. Local folders are unaffected by this. What can I do? I have Thunderbird 24.5.0. Thanks for any help.