I did some further research and started the webshop on various laptops, desktops and also on an IPad and they all gave the same result!
If I indicate to the administrator "Language" English (United Kingdom), the VAT is shown as follows: "(Incl. Tax €7.81)".
If I indicate to the administrator "Language" Dutch (nl-NL), the VAT is shown as follows: "(Inclusief btw undefined)".
Login as Administrator and goto EasyStore -> Orders -> And select order #29 and see the problem!
Also very strange how the product now is displayed!
Aanbieding! Kat - Surprise box - Vlees (variatie van 24 blikken) - 24 x 200 gram €45,00
€45,00 x1 Inclusief btw
undefined
€45,00