Is this a "it worked before but not now" or "it never worked before" type issue?
If you were able to open 13 before, did you update it to 13.1 using an opened project's Help Menu/Updates?
What is your Mac operating system? Are your computer updates up to date and is your computer optimized?
Are you running the programs as administrator (from user account with administrative privileges)?
Latest version of QuickTime 7 installed on your computer?
Are you running the program on an individual computer or from a school or company network?
Is your video card/graphics card driver version up to date according to the web site of the manufacturer of the card?
Do you have many 3rd party plug-ins and/or codecs installed on your computer?
Let us start here, and then decide what next based on the details in your reply.
yes it worked before.
my mac operating system is OS X El Capitan 10.11.2 up to date and optimized
running as administrator yes
quick time 7 installed
it is a relatively new computer so there are not any 3rd party plug ins