LIFX did some cloud work and right after that, I noticed my link to ST was no longer there. I also lost control of all LIFX lights via ST, but not Alexa. Based on that, I took a look at the link within ST and noticed it wasn’t logged in any more. If you are having issues, you might need to log back into LIFX via the ST app to re-link them. It looks like the cloud-to-cloud link dropped during their maintenance.
ST staff members have conveyed that ST Classic will remain available until all equivalent functionality is available in the new app. From what we see visible, they are only 1/10 of the way there, if that. I’m sure a version is in Dev has more bells and whistles applied to it.
For now, unless you are a Samsung Connect Pro customer (have a v1 or v2 hub), there is no reason to use/configure anything in the new app as it barely has any functionality built in.