How to do a fresh re-install of Ecommerce?

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Hi,

We have Ecommerce installed with digital downloads and we recently started getting this problem:

https://www.concrete5.org/marketplace/addons/ecommerce/support/check...

We've not got a response from support and need to get this fixed ASAP. Can anyone advise on how to re-install Ecommerce without ruining the current installation?

Thanks,
Millo