Macs are pretty good at choosing the right application to open a document. For example when you double click on a .nucl document then it will open in MacVector. However, sometimes this file association breaks. Applications should coexist peacefully on a Mac, but sometimes a misbehaving app will corrupt these file associations and you will find that your sequence displays a generic document icon (or what’s worse a different application!). When you double click on the icon, it will no longer open in your favourite DNA sequence analysis tool!
Luckily this is easily fixable:
Repeat for all file types used by MacVector that are not opening correctly (e.g. .prot, .msan, .msap, .axml)