Currency reverts to default during the checkout process + Auto-update

Our website has the EUR currency per default. When the CHF currency is chosen, the plugin correctly displays the product prices in CHF, however when entering the check out page, it reverts to EUR so it is basically not possible to pay in EUR. Could you help us rapidly to solve this issue?
Other than that, I paid for renewing the auto update for this plugin on Friday and it does not auto update. Could you please check it?
Thanks in advance & kind regards,
JC