If you are upgrading the theme to a newer version, there is a chance that we updated the bundled plugins as well (especially the Revolution Slider).
Since Revolution Slider supports the updates within the slider itself, you should locate the installable zip file called revslider.zip.
First go to ThemeForest > Downloads and download the Installable WordPress file only. Then unzip it in your computer and you will find the revslider.zip for different themes in:
- For Hairpress: in tgm-plugin-activation/plugins/revslider.zip
- For Dining Restaurant and Webmarket: in bundled-plugins/revslider.zip
Then go to your wp-admin > Revolution Slider and at the bottom right corner of the page you will notice the button Manual Plugin Update:
Click on it an upload the revslider.zip file from there.