A new location starts from nothing in the two things that matter most locally, and only one of them can be hurried.
The page is the easy part and the part everyone does first. The profile, the reviews and the entity are the slow parts, and they are what the map pack is actually reading.
Work through it in this order
Is there a separate profile with a real address?
A second location needs its own profile at a real staffed address. Adding a town to your existing service areas does not create a presence there.
Owned by Local SEO
Is the address genuinely staffed?
This is a policy question as much as a ranking one. A profile at an address nobody works from is the most common cause of a suspension.
Owned by Local SEO
How many reviews does it have?
Reviews belong to the profile, not the company. A branch with four reviews competes against neighbours with two hundred, and this is the constraint that takes quarters rather than weeks.
Owned by Local SEO
Does the page say anything true about that place?
A duplicate of the main service page with the town swapped in is the pattern Google names in its doorway policy.
Owned by Content
Expect the page to be the fastest part and the reviews to be the slowest. An agency promising map-pack presence for a new branch inside a quarter is promising something reviews will not allow.