First be sure that the file you are importing is a supported format by Camtasia Studio. See the article below for a list of supported formats.
Which file formats can I import into Camtasia Studio
If you are importing an MP4 file be sure that it is encoded in the H.264 codec. That is the only codec that will work when importing MP4 files to Camtasia.
If you are importing an MOV file please see the following article.
If you are importing an AVI file be sure that the codec the AVI file is encoded with is installed on your machine. For example, if the AVI is using the Xvid codec you must install Xvid on your machine.
If you are getting this message with a TREC file it's possible that file could be corrupt. Please submit a ticket to see what we can do to possibly recover that TREC file for you.