I cannot find how to start a new topic in this forum.
Please see this screenshot which shows where the link is to create a new thread.
It did not have the file 'JuiceboxBuilder.air'
If you would like to check that your 'juicebox_pro_1.4.2.zip' file is complete and not corrupt, you can check its file size and MD5 and SHA1 hashes with a program such as HashCalc (free). The zip file should have the following properties.
juicebox_pro_1.4.2.zip
Filesize: 1,731,520 bytes
MD5: d9b0ea9db1be174e3bea5bb678c7a003
SHA1: 0c550f7ab43fb3a2f03d53ad88a93f7fa5df6cbf
If the properties of your downloaded file match those above, then you have the correct and complete Juicebox-Pro package.
It is unlikely but possible that an anti-virus program may be quarantining the contents of the zip file as soon as it is extracted so try temporarily disabling real-time protection in any security software that you have installed.
Also, you could try extracting the zip file using a different program. Both Mac OS and Windows can natively extract zip files but you might like to try a third-party program such as 7-Zip (free).
If the properties of your downloaded file do not match those above, then please try downloading the file again using a different browser (Chrome, Firefox, Internet Explorer, Opera or Safari).
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