There currently are 2 known issues in Autoptimize 2.7.5 that will be fixed in the next release;
- when “inline & defer CSS” and “also aggregate inline CSS” are active then for logged in users the top “admin bar” might become invisible. unticking “also aggregate inline CSS” is a confirmed workaround.
- when “inline & defer CSS” is active, CSS-files that are not aggregated (excluded or 3rd party) and that do not have a media-attribute will not be deferred.
If you want you can download the beta of what will become 2.7.6 here and install that instead of 2.7.5 to get rid of these known issues.