@Jessica4284
Yikes! It does look like you are supposed to have collected an 8% Occupancy Tax from guests and paid to the county quarterly?
San Diego County Transient Occupancy Tax
https://www.sdttc.com/content/ttc/en/tax-collection/transient-occupancy-tax.html
The county doesn't have to work too hard to see all the Airbnb listings in Alpine, CA and determine if they have been paid by the Host. They can just search Alpine, CA and see all the listings. Airbnb says they may share information about your listing to tax authorities:
How Taxes Work For Hosts
https://www.airbnb.com/help/article/2523#section-heading-3-1

My suggestion would be to calculate what you owe and pay it. See if the County will waive the fines. You may be able to write off what you have to pay as a business expense, but I would run that by an accountant.
Going forward, you may be able to add a custom tax to your listing for the 8% tax so the guest pays that as part of the total booking. Airbnb will pay you and then you pay the county according to their schedule (looks like quarterly). You do need to turn on Professional Tools in your Account Settings to see if Airbnb allows you to add a custom tax to the listing. If you don't see the option to add a Custom tax, then you would have to collect the tax manually from each guest after booking...a real pain. The other option if Airbnb doesn't allow you to add the custom tax is to add a "Community Fee" to your listing and explain that is the required occupancy tax on the listing somewhere. It will increase your nightly rate, so if other Hosts aren't do that, you will be priced higher than them.
Add A Custom Tax
https://www.airbnb.com/help/search?q=add%20a%20custom%20tax