Hi -
I last checked (before your post) the very day they rolled out the new website. Hoped it would improve over time.
I just now checked some dates for the reservable period (summer-September end, IIRC) and ran into abundant frustrations.

During the earlier check, I noticed that reservations for some sites within the system would not open until a couple of months into 2020. I do not find the relevant message now. It is possible that message applied to Berg Lake trail (I checked only 3-4 trails/locations). The new Discover Canada res system feels as though it is still in beta testing. I hope the Berg Lake calendar is restored.
In the meantime, would calling the number provided help?

BTW, res system for Lake O'Hara has completely changed. Jan 24, 2020, online reservations for campground open 8 a.m. MST for entire season. Bus res is a random draw from people who enter online lottery during month of Feb.

I really hope Discover Canada overhaul gets completed, or fixed, soon.

Good luck!