hello @romakim welcome to the forum 
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This will give us the technical info and logs needed to help you in case the machine in question in spitting out errors! Since you’ve provided zero technical details it is impossible to help you as-is. Thanks.
Please use the search - lot of issues have been discussed already.
Good starting point for Office issues is here Nextcloud Collabora integration. Built-in Code is slightly different but general mechanics are same application docs show prerequisites and some additional details.