Hi Giorgos,
I apologize for not explaining the details in the post above.
You can check “Site Actions”, select “Site Settings”, Click “Site collection features” as the screenshot shows below:
Compare these features with the SharePoint 2010 on-premise features and check if they are matched.
In addition, you can try the steps below to clarify the issue:
1. Try to export a list temple which is not a custom list to clarify if the issue is related to the list type.
2. Try to create a new site collection and test the list template to clarify if the issue is related to the site collection.
Thanks,
Wilfred Ying