At some point today, Cabin 2 (Finn, Peter Pettigrew, Tony Stark (MCU), Bucky Barnes (616), Toby Williams, Peter Parker (MCU), Kira Manning) will notice that Shuri is missing.
Cabin 10 (Barbara Gordon, Darcy Lewis, Max Eisenhardt, Lois Lane, Courier Six, Wanda Maximoff, Michelle Jones) will notice that Max Eisenhardt is missing. Because Max is the only ECHO in Cabin 10, while he's gone the Cabin must rely on other Cabins if they need medical attention. They can no longer access their own supplies.
Cabin 4 (Sirius Black, Riri Williams, Logan, Bruce Banner (616), Groot, Regina Mills, Kamala Khan) will notice that Steve Harrington is missing. As Steve is the only Lima block specimen in his cabin, no one will be able to read the map in that cabin.
The Upside-down
To return to the land of the living, Max, Shuri and Steve must Complete a Upside-Down prompt.
This can be done through communications with Romeo, a log or a narrative. Those who were taken by monsters (Regulus, Howard) will remember their abduction. Those who were killed by their own story prompts (Victoria) will remember how they died.
Remember, there is no network access in the upside down. They can only communicate through a divination post with someone in Romeo.