Bike creaking when pedaling hard
It could be a couple different things but new bike and metallic click plus only happening pushing hard on the right crank points to a very high likelihood of the chain rubbing against the front derailleur cage. This could be caused by either or a combination of:

The front derailleur cable has lost a little tension, which is common as bikes break in. Solve by tightening the barrel adjuster, which is easy to search for here.
The front shifter has trim stops you're not using properly. Again there are many questions about this here. This is more consistent with a shop getting it back and spending some time on it and the noise still persisting. Shop people will use the trim stops without thinking when they test ride a bike. Making sure trim usage is gone over with each customer is something that can fall between the cranks in sales and service interactions, and complicating matters is that some customers vibe like they don't want or need to be taken to school.
The front derailleur high limit screw might be too far in, although depending on the bike/crank/chainline/chainrings it could be how it is for a reason.