Advice needed on afternoons

Small breed puppy is 12 weeks old, has been home w us for three weeks.

Set up is a playpen downstairs with sleep tent (in lieu of crate). Sleep tent comes up to bedroom at night pup sleeps through night with a wake up around 1 am for pee then back to bed until 5

Pup does well with enforced naps during day, settles within a minute or two no issues. Pup is okay being left at home for 3-4 hours if needed for work. Between naps there’s potty play training etc, try to ensure pup is only up for 60-90 mins until next nap.

After 3 pm though, cannot get pup to spend time alone in crate or engage in nap and then pup becomes hyper, nippy, and overstimulated until bedtime at 6:30 pm. Have tried Kong, other toys, free roam downstairs etc but pup will cry, will not settle on own, and it’s just like a 3.5 hour bad zoomie until put him down at 6:30.

Any advice would be greatly appreciated as it’s been hard to manage 3-6:30 pm for about 5 days now.