I have the Firefox Multi-Account Containers extensions installed, and configured with 3 containers: one for YouTube, other for Amazon, and finally one for Facebook and Instagram. Each container only opens said website and also logs-in to said website. I also have another computer with Firefox which all of those settings are also synced. Both Amazon and Facebook work perfectly, but the Facebook container constantly logs out both from Facebook and Instagram, prompting me to enter my credentials time and time again, which has reached to the extent that now Facebook presents a Captcha every login, alongside a prompt asking me if I want to save those login credentials (which I say yes). This started to happen last week as I did a fresh install of my OS on my desktop rig after I logged in into my Firefox Sync account and configured the Firefox Multi-Account Containers extension. And yes, I have disabled erasing cookies after I close Firefox, Allow cookies and site data, and added both Instagram and Facebook as explicit options to save those cookies. EDIT: I also noticed that this happens whenever I open up Facebook/Instagram on the other device (PC/Desktop, and as long as I'm still using the same device, the session is still open.