"nothing works" is exactly right........did read one post that said "upgraded to Sierra and it worked" have not taken that leap yet though.
You're most likely experiencing the same issue reported at Adobe flash player, How to fix Flash installation fails at 90% , and Adobe Flash Installer (version 188.8.131.52) hangs at 90% on my iMac. To verify, I'll need to review the install.log and FlashPlayerInstallManager.log files. Please review the FAQWhere do I find the Flash Player installation log on the Macintosh? and configure your system to obtain install.log and FlashPlayerInstallManager.log files for the Flash Player installation. Repeat the installation until it returns the error so the logs captured are for the same installation attempt. Upload both log files to cloud.acrobat.com/send using the instructions at How to share a document and post the link to the uploaded file in your reply.