Hi @Timothy694
If you are using professional hosting tools, the answer could be more complicated.
However, if you're only using the straight-forward Airbnb calendar, check the following:
Go to the Availability tab and click the block that says Minimum nights. I know you say this is set to 1 night, but you also have to check whether every day of the week is set to 1 night. So click through to "Customise by check-in day" and make sure they are all 1 night.
Next, go to Custom trip lengths (just below the maximum stay). Check that you haven't perhaps set a different minimum stay for these particular date ranges.
Then, go to Preparation time. This is the section that @Kathy1371 mentioned. It is also on the Availability tab, just one field below Custom Trip Lengths. Here you need to make sure that the preparation time is set to None.
If your dates are still not bookable, also check More Availability Settings (just a bit down from Preparation time). Make sure all the days are unticked, otherwise the system won't allow guests to check in on that day of the week.
Hope one of these solves the issue!