"This content requires the Adobe Flash Player. Get Flash."
Here's a simple 4 step solution:
Step 1: Just click on the leftmost area of the address bar - where you see that the connection is secure; to view site information.
Step 2: If 'Flash' is not listed in the drop-down that you see, click on 'Site Settings' option.
Step 3: Locate Flash in this settings page and change the default option of 'Ask' to 'Allow'
Step 4: Reload the page to check if your preview works fine now!
Note: If you already see 'Flash' option after step 1, just use the drop-down to change the value to 'Allow'
Simple as that! Did this trick work for you? Let us know in the comment section below.