Can you try to run a quick test and try to trigger a backup manually directly in UpdraftPlus on the child sites, after the backup completes, please check the WP > Settings > MainWP Child > Child Reports page and see if the backup shows up in the table? Let me know how that goes.
Just chiming in that I have the exact same issue. Seems manual backups record but automatic do not for UpdraftPlus Premium.
I’d been using the Reports extension for months with no problem, but it happened last month, thought it was fixed, but happened again. Unfortunately found out after automatic reports went out. (Yes, I have a ticket open.)
Let’s try to limit the “same here” and “me too” posts in the community it just makes it harder to track and keep up with the topic, especially if @staff member says they are working on it.
Just a quick update to this problem, today we released the MainWP Child Reports plugin version 2.0.3 that solves the problem of logging UpdraftPlus backups. As soon as you update the plugin, it will start recording new UpdraftPlus backups.