Zend certified PHP/Magento developer

Disable URL rewrite for specific URL

I have the ShipStation extension installed in my Magento store (v2.4.4), and I’m having a problem with the APIs. ShipStation tries to connect at www.mystore.com/index.php/api/auctane, but with with web server rewrites enabled, there is no index.php in the APIs URL. I tried the following:

RewriteCond %{REQUEST_URI} ^/index.php/
RewriteRule (.*)index.php/(.*) /$2 [L,R=307,NC,QSA]

It worked for configuration (POST), and it works for exporting orders (GET), but it won’t work for shipment notifications which is also POST. It seems that it isn’t redirecting. Is there a way to disable rewrites only for this specific URL?