alright, I've found a workaround for the issue i was having with private collection pages not displaying, but it also raises other questions about the way the Itch app is working and potential security issues. it appeared to be due to not being signed in (having permission) to view the information in the Itch app browser, even though i do sign in with my username and password to the Itch app itself. so, i clicked on the Itch.io tab under BASICS, then I used the LOGIN button to log into my account again inside the browser in the Itch app. closed the tabs for my collections that were broken, and reopened them (Why are collections even listed under My Creations now? I presume they're typically used to organize games that are mostly not "my creations"). this solved the problem for now.
i tested exiting the Itch app and signing back in, and it maintained my login within the Itch browser. i suppose this is good, since it will only force anyone to do this once to fix the problem - or the app can do it automatically since the user enters their username and password to connect to their account with the app. BUT, I did notice that the Itch app saved my login credentials, so it is now possible for anyone with physical access to my computer to gain full access to my Itch account using the Itch app browser (the in-app URL bar allows you to go wherever you want - delete my account? change my payment email address and intiate a payout?).
This seems like a potentially serious security issue - can I have the option to forget my credentials between sign-ins if the app is going to be this deeply integrated with my account? I note that right now, there is an option to LOGOUT in the app, but if you do that, there is no request for password or username to log back in. This should be changed, and there should be an option to automatically log out every time the app exits.