This sounds (perhaps) as if the audio may be too long for the project rate.
You could try opening the project in 2.0.6-alpha (get the build from the top of gaclrecords.org.uk ).
This issue (if it’s the cause) is explained here:
Missing features - Audacity Support .
If the project does not open correctly in 2.0.6-alpha, please attach (1) the AUP file and (2) the log file from Help > Show Log… (top right of the Audacity menus).
Please see here for how to attach files: https://forum.audacityteam.org/t/how-to-attach-files-to-forum-posts/24026/1 .
Gale