You can validate Your XML document for EN 16931-1:2017 (for B2G customers) on our site https://legacy-mer.moj-eracun.hr/exchange/validateubl
The are multilple options but for validating EN 19631-1:2017 eInvoices and eCreditNotes, use the last one from dropdown (Kompatibilnost za slanje eRačuna prema EN 16931 za državu (UBL 2.1 Invoice).
New XML structure EN 16931 + HR CIUS 2025 (for B2B customers) can be validated on our new site https://validate-demo.moj-eracun.hr/Validation/ValidateUBL . Currently on a UBL validator you can upload eInvoice and eCreditNotes.