There are a few causes to orders not populating under the MXED Order Page.
The most common reason is that the product was not imported with MXED. For instance if you duplicated an existing product. You can verify your synced products on the Live products section within MXED then click the "Open in Shopify" button
The product was manually created on the Shopify platform vs adding the product from MXED.
Removing or adding product variant data. This may affect the sync because MXED dosen't know which variant you are selling in your Shopify store.
Please make sure the MXED Product have the MXED tag on your Shopify store