If you have a project that no longer opens in the latest version of Construct, send it to us at supportkho@construct.net and we'll take a look. However I'd note it's not always possible to help, as problems can be caused by things like hardware failure causing data corruption, bad third-party addon updates breaking projects, and other outside causes.
It would also useful to go through the releases page and find whether it really does still open in old versions (in which case you have a workaround for the time being), and which specific version it stops opening in (which is very useful information to have with any issue report).