Yoast plugin not working on many of our WordPress sites

This is a re-post because it’s not the theme, because the sites affected have different themes (I was thinking they were all headway, so it looks like not).
It may be a bug in the plugin, it may be a conflict with another plugin.

Are there any known conflicts with other plug ins that could cause the yoast plug in ‘s focus keyword not to stick or the content analysis to populate?
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