First, find out what you mean by not showing up
There are two different lists. The map results come from your Google listing, and the regular results come from your website. A business can be in one and missing from the other, and the fixes are different.
Open a private window so your own history does not colour the answer, and search for your exact business name with your town. If your site or listing appears, Google knows you, and the question becomes why you don't appear for what you sell. If nothing appears, start with the next two steps.
Is your site on Google at all?
Search for site: followed by your domain, with no space, such as site:example.com. If that returns nothing, Google has not put your site in its index. Google's own guide starts with the same search.
The usual reasons are a brand new site, a setting that tells search engines to stay away, and a page Google cannot read. Search Console is free and shows which of your pages are on Google and why the others are not. My free check also looks at this, and the part about being found takes less than a minute.
Do you have a Google listing?
Without a Google Business Profile you will not appear in the map results. Search for your business in Google Maps. If you find it unclaimed, claim it. If you find nothing, create one, and expect Google to verify that you are real before it shows.
If you visit customers and don't have a shop, you can still have one. Google lets you hide your address and show the areas you serve instead. It still needs a real address to verify you, and a PO box won't do for that.
Does your site say what you sell and where?
I see this often. I ran my check on 195 business websites in Los Gatos and Campbell, and 105 of them did not put their town in the page title or main heading. 105 had a search description that was missing or too long to show whole. 64 had no structured data, the form that states your name, address, phone number and hours for search engines. The findings page has the rest.
Read your home page title as if you had never heard of your business. It should say what you do and where. "Home" or your name alone says neither.
Do your details match everywhere?
Look at your name, phone number and hours on your site, on your Google listing and on any directory you are in. My Google listing check compares your listing with your site for you.
If all of that is fine
Then the rest is competition and time. Google says local results depend mainly on relevance, distance and prominence. Prominence comes partly from reviews and from other sites that link to you, and those build up slowly. Distance can't be changed, so a business rarely ranks on the map far from where it is.
Be careful with anyone who promises first place. Google says there is no way to request or pay for a better local ranking.
The quick way to check most of this
The free site check runs most of these checks on your site at once and lists what to fix first, in about half a minute, with no sign-up. If you would rather have it handled, local SEO is what I do for businesses across the Bay Area.