Hello @Robyn64,
Just some possibilities ...
Have you sent a pre-approval to this of another guest for some or all of those dates? If so, remove the pre-approval.
If the dates are in the very near future could it be that they are within your advance notice period?
Are they close to a previous or following confirmed reservation. If so, it may be that they're clashing with your preparation time setting.
You can see your sdvance notice and preparation time settings under your calendar's "Availability setttings" and then "Reservation preferences".
If the above doesn't explain it then contact Airbnb customer services.
Steve.