Getting the "Maybe wrong folder permissions" -- Membership Pro 2

Hi there. I am trying to install the Membership Pro 2 plugin, but I keep getting the "Maybe wrong folder permissions" error message. Here are the steps I've followed, which I got from your support site:

1. Disable the WPMU DEV Dashboard via "Plugins -> All plugins" page
2. Access your site by FTP
3. As you already downloaded WPMU DEV Dashboard plugin .zip archive (make sure that's the most recent release), extract it to your local storage
4. on your server go to "/wp-config/plugins" folder
5. delete the "wpmudev-updates" folder
6. upload the "wpmudev-updates" folder from extracted archive from your local storage to "/wp-content/plugins" folder on your server
7. enable WPMU DEV Dashboard plugin in your dashboard again

If this doesn't help:

8. access your server via FTP again
9. make sure again that permissions for /wp-content/plugins folder are set to 0755. Depending on an FTP client you're using you may want to instead set permissions "verbally" where:
- 0755 stands for "read + write + execute" for owner, "read + execute" for group and "read + execute" for others.

Neither method helped (the settings are correct on the FTP site). I should note that I'm able to install other plugins just fine. Any ideas about what may be going on? I've allowed access to the website if needed.