So in my original Thunderbird I had a folder with all my client emails (it's huge, about 2.8gb). I followed the instruction video to migrate my Thunderbird data over to my new laptop (both systems are Windows 10 if that's relevant) and whilst it was mostly successful and the local folder is shown, none of the subfolders are. However, when I search for a client email address it gives results that would be in the missing folder (and lists the missing folder as the source). How can I get the folder to be visible again? I do access the folder regularly to reference client orders.

Yesterday I was able to copy one of the smaller folders to a gmail account so I can copy them back onto my new laptop and that worked. I tried this again today with the larger, more important file and it's just not letting me copy files at all. Any input on why this is happening would be very appreciated. I guess it's possible that it's just making the transfer in the background so looks like it's not doing anything? Thanks in advance.