Most of the used items available to buy on the MPB platform are sold under the Secondhand VAT margin scheme. For more information on the scheme see here.
For items sold under the VAT margin scheme there is no applicable VAT to be claimed back, and no VAT amount will be itemised on your invoice.
Some used items, and all new items such as accessories, available on the MPB platform are sold under the standard VAT scheme at a rate of 20%. For these items you will see the VAT amount on your invoice, and this can be claimed back in the usual manner.