I'll need to get the online installer log files from you to troubleshoot the error. Please do the following:
1. Select the Go -> Go to Folder... menu item from the Finder menu
2. Copy and paste ~/Library/Logs/Adobe_ADMLogs into the Go to Folder dialog
3. Locate the Adobe_ADM.log and Adobe_GDE.log files in the folder that appears.
4. Upload the 2 files to cloud.acrobat.com/send using the instructions at How to share a document
5. Post the link to the uploaded files in your reply.
I updated Max OS with the last version 10.11.6
I apologize for not replying sooner. I was on vacation and just returned. I do see an HTTP connection error, but am not too familiar with it and will need to forward it to the online installer team. Essentially, the online installer downloads and installs Flash Player silently in the background. For some reason, this download is failing.
In the mean time, please try using the offline installer posted at the bottom of the Installation problems | Flash Player | Mac in the 'Still having problems' section.
Thanks Maria !
The offline installer fixed it !