403 Forbidden on Postcode search

Receiving a 403 forbidden error when searching for a postcode using the calculator.
When the calculator is not present (simplified mode) I receive a “Please sure postcode/suburb is selected)

Please advise – ERROR BELOW from console:

jquery.min.js?ver=3.5.1:2 GET https://scrapltd.com.au/wp-content/plugins/transdirect-shipping/includes/locations.php?q=2912&requestNumber=7 403
send @ jquery.min.js?ver=3.5.1:2
ajax @ jquery.min.js?ver=3.5.1:2
s.ajax.s.ajax @ jquery-migrate.min.js?ver=3.3.2:2
S.<computed> @ jquery.min.js?ver=3.5.1:2
getJSON @ jquery.min.js?ver=3.5.1:2
td_autocomplete @ (index):522
(anonymous) @ (index):501
dispatch @ jquery.min.js?ver=3.5.1:2
v.handle @ jquery.min.js?ver=3.5.1:2

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