For imports there 4 condition types need to be keyed in while creating a PO,Like JADC, JCV1,JEC1 & J1CV.If the supplying vendor is coming in MIRO then please check in PO by selecting the condition type starting with J & click on the lens icon & see whether you have keyed in the CUSTOMS VENDOR.
I hope you have missed for atleast for one condition type. Then i MIRO you have select only the Planned delivery cost option it should definitely work