There are a variety of reasons why Sentinel-2 data do not open as discussed in this help article:
http://www.harrisgeospati...s-in-ENVI-53531.aspx Sometimes it is caused by very long path names on Windows and it is also caused by a constantly changing XML format by various distributors. We are addressing these issues as they arise. The best option is to update your software to the latest version. ENVI 5.4 fixed several issues in ENVI 5.3 SP1/Sp2 and there will be further format fixes with the upcoming service pack for ENVI 5.4. If you still have ENVI 5.3 and are not able to upgrade to ENVI 5.4, then you should at least obtain the service pack for that version.
http://www.harrisgeospati...count/Downloads.aspx