I am not sure I understand. Are you renting your unit exclusively through Airbnb? Or, are you using other platforms as well? All short-term rental stays in St Johns county are taxed 10.5%, but how it's paid by the host depends on what platform you use.
If your guest comes to you via Airbnb, then you and your manager should NOT be charging the guest the Florida State Sales Tax and Surtax of 6.5%. Airbnb does that for all Florida hosts. That would be double taxation.
However, Airbnb does not collect the St Johns county Transient Tourist Tax (aka Bed tax). You must collect this from the guest, or pay it from your earnings. This tax is to be paid to the county on a monthly basis. Currenty, it is 4% but the commissioners are talking about raising it.
Is your manager really collecting this tax from the guest or is it absorb in your nightly rate? If the guest is not paying 4% on top of your nightly rate and cleaning fee, then your manager needs to collect it from you.
Do you have the county's business license? If yes, the county's tax collectors office will provide your manager with the forms you need to submit the tax. Ask your manager if s/he is using those forms.
If you do not have a business license, have your manager get one soon. You will need to pay any back taxes, but they will waive late fees.
Hope this helps. - Karen