Save plan is ... not saved

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https://abrp.upvoty.com/b/report-a-bug/save-plan-is-not-saved/
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I created a plan for a trip through Sweden. Went to Save it, selected the waypoints (shouldn't that be the default?) and hit Save. OK. But then if I go to Saved Plans, it doesn't appear.

I seemed to finally get something to save by not selecting any of the waypoints (including a ferry). But definitely something very weird going on, or the logic is obtuse.

This is on the desktop version of the site, in Safari.