How to restore access to a TrueCrypt container?

Question

TrueCrypt

There is an encrypted TrueCrypt volume in the form of a container file.
The volume was mounted and used in Win7 as a regular logical
drive. At one fine moment, they connected a portable
hard drive (500 GB) to the computer, the system asked, for some reason, to assign a volume letter to it,
and on the machine, they assigned the letter under which the TrueCrypt volume was
(at that time it was open and used in Win7 as a normal
logical drive) Windows began to perform some actions and
everything was immediately canceled by the user, but after that, when
opening the container file, it appears: "The file system present on the volume cannot be recognized
. Make sure that all
system drivers are loaded, as well as in that the volume is not damaged."
What to do in this situation? We tried all the programs that
get the information, nothing comes out. Anyone can help?