[Решено] Product variations disappear after activating WooCommerce Multilingual & Multicurrency

Background of the issue:
I am trying to use the WooCommerce Multilingual & Multicurrency plugin with my WordPress site. When I activate this plugin, the product variations disappear. This happens when I create a new product, add variations, and then click on 'Publish'.

Symptoms:
After activating the WooCommerce Multilingual & Multicurrency plugin, the product variations disappear upon publishing.

Questions:
Why do product variations disappear after activating the WooCommerce Multilingual & Multicurrency plugin?
Is there anything we can try ourselves to resolve this issue?