I also posted it on Github but then thought it might not be the best place for a ‘Pro bug’.
I noticed my Yoast admin menu bar item was missing the past days.
I then switched back to Twentyseventeen and started activating plugins one by one.
When I activated ACF (Pro), it made Yoast’s menu item disappear.
I tried other situations as well to eliminate if it was something else, but to me it appears to be ACF latest update.
I retract my message… There was a small mu plugin which I overlooked which had a function which removed it when ACF was active.