I have a version of InDesign CS5 logged against my Adobe ID which I use infrequently but I still use. I went to open a previously created ID file today and discovered that whilst my version will open it says it can't find a number of plug ins and then trys to take me to a link to subscribe to CC.
How can I continue to use my fully paid for and previously adequate ID CS5 software without having to agree to a CC subscription?
Did you ever install a trial of InDesign CC? Or could that file have been modified by someone who had a copy of InDesign CC? The "missing plug-ins" message usually points in that direction: the file has the format of an InDesign CC file.