After platform was updated, you should update all your active plugins to solve 500 error. That's all you need to do.
As usual, plugin's update can be performed automatically or manually.
To make update more safely for you, it is recommended to wait until auto update requests will be appeared for all you plugins.
P.S. Don't forget to update your theme at the end.
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Updated
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If you see somewhere on your site 500 internal error, then:
- enable DEBUG_MODE by setting this variable in TRUE position in ow_includes/config.php file;
- reproduce an error again on your site;
- search the forum for this error;
- if search was failed, create a separate topic with including the whole text (screenshot) of an error and pointing conditions (page, user actions) to reproduce it.
Following these easy steps you will really help us to detect an issue faster and provide you with solution.
Thank you for understanding and cooperation!