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Hi  giuliapiazza94 ,

Does your two tables have some kind of dependency, one referencing the other?

For example, if you want to merge table A and table B, but table B itself is merged from table A with other tables. At this time, table A and table B are merged. Will show an error like this.

https://community.powerbi.com/t5/Power-Query/Not-being-able-to-merge-two-tables-in-Power-Query/td-p/1127628

You can also update power bi desktop to the latest version.

Best Regards,

Liu Yang

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