I have installed the forum and created a custom child forum that I could modify. I got it all setup when someone is logged in but if a user logs out everything in the tags goes away. While logged in everything is fine, I couldn't find any if statements where the user needed to be logged on to show the CSS. Is it calling a different theme when the user logs out?
I am currently working on EE3.5.7 with discussion forum installed. I also created a custom theme for the forum and I didn't have an issue like this. Whether logged in or logged out, the CSS is okay.
Can you provide more details as to what tags are not being parsed if user is logged out? and at what page does it happen?
PS: Sorry, I wanted to leave a comment, but my reputation is low.