Why can't I update Adobe flash player now that I have upgraded to Yosemite?

Look in your downloads folder, find the file that just downloaded, and double click to mount the .dmg (disk image). A windows opens after half minute or so with the Installer icon in it. Then double click the Installer and check some checkboxes and it will Install.

I have never seen mine install "automatically". It always seems to require this same drill.

Try:

How to perform a "clean install" of Flash Player in Mac OS X

However, it could be a malicious site putting that message up trying to get you to click on the button to install malicious software on your computer.

Go to Adobe's site and check to see if you have the latest Flash.

You can also go to System Preferences>Flash Player and check for updates and install themthere

First, use this Adobe website to check to see if you really need to update. If the installed version is older than the current version, you can download the latest installer directly from Adobe and run the installer locally.

Flash Player should ONLY be installed from Adobe’s website.

You can check here what version of Flash player you actually have installed: http://kb2.adobe.com/cps/155/tn_15507.html

You can check here: http://www.adobe.com/products/flash/about/ to see which version you should install for your Mac and OS. You should first uninstall any previous version of Flash Player, using the uninstaller from here (make sure you use the correct one!):

http://kb2.adobe.com/cps/909/cpsid_90906.html

and also that you follow the instructions closely, such as closing ALL applications (including Safari) first before installing. It is highly recommended that you carry out a permission repair after installing anything from Adobe.

After installing, reboot your Mac and relaunch Safari, then in Safari Preferences/Security enable ‘Allow Plugins’. If you are running 10.6.8 or later:

When you have installed the latest version of Flash, relaunch Safari and test.

If you're getting a "blocked plug-in" error, then in System Preferences… ▹ Flash Player ▹ Advanced

click Check Now. Quit and relaunch your browser. More advice here:

http://www.macworld.co.uk/how-to/mac-software/unblock-safari-plug-ins-on-mac-360 8065/

A genuine alert that Flash is outdated and blocked is shown on this page. Follow the instructions on the page in that case. Otherwise, the alert is not trustworthy and someone may be trying to scam you into installing malware. If you see fake update prompts on more than one website, or if you've already followed one of the fake prompts, ask for instructions.