This issue is due to the way MercadoPago plugin returns its status, which was always interpreted as disabled by the Currency Switcher prior to version

To solve the issue, please update the Currency Switcher to version or newer. Also, please make sure that you are running MercadoPago plugin version 1.7.0 or later.

Thanks to Claudio Sanches for developing the MercadoPago plugin and for his contribution to solve the incompatibility issue.

Further reading