Summary: This bug happens on Live and PTS (latest update was on the 10th of October). Probably it's related to Auto-Recruit option (update - October 8). These options will work again if squad leaves platoon. Screenshots: Squad UI. Platoon UI. You can notice that it doesn't have Auto-Recruit option (or more likely option is here but "Auto-recruit" words doesn't show up). "Disable recruitment" and "Enable recruitment" is superimposed. If private squad option is ON, you can press it after joining platoon but nothing will change. If private squad option is OFF, you will be able to press mute platoon (though I didn't check if it works)
Fixed. December 17, 2019 - Spark and Snow (PC Update): Platoons can once again enable squad recruitment outside of Alpha squad.