Class 'WPSEO_OnPage' not found

After update to 3.0.1 same problem

Have you manually overwritten the plugin files or removed the plugin and uploaded it again?
This issues sounds like there is (at least) one file missing.

Both first manually overwritten and then removed and reupload the pplugin files

all files on the server are the same like in the plugin package

If all files are as in the zip-file, there can be no reason why this doesn’t work.
Unless your server is caching very aggressively. Are you able to clear all caches on your server?

that was the first thing I’ve done. Also, I’m caching temporarily disabled.

hm strange as it does not impinge on a separate page (the same server, same plugins)

Hello,

i have the same problem.

I installed YOAST and activate it and it works well… then i deactivate it and 10 minutes later i want to reactivate it again and i got the same error.

Fatal error: Class ‘WPSEO_OnPage’ not found in /DOMAIN/subdomains/www/html/wp-content/plugins/wordpress-seo/wp-seo-main.php on line 353

I have found this exact same error. And for me what it’s doing is messing up something with the canonical urls. With the www works, and without it doesn’t (across browsers). We’ve been using this plugin for a long while and had no issue. So not sure if it’s compatibility with the new version of WordPress that’s the issue?

We have GoDaddy’s Managed WordPress hosting package, and initially toggling off and on which was the primary web url worked (without www / with). But it’s happened again now. I’ll post an update if GoDaddy has an update for me.