Hi Leonardo Quinteros,
As per the description, it seems like the "Export to Excel" button in SharePoint Libraries is missing and it is happening on other users in your company. If my understanding is correct, I tried to test across my multiple tenants with existing and new libraries but all failed to reproduce the behavior.
Then, I helped to check in Microsoft Service Incident, and it seems like currently there has no related SI about the missing option but mainly about the delay SharePoint sites loading. In this situation, I would suggest you contact the admin to check in Microsoft Admin Center from your tenant and see if any related SI is listed: How to check Microsoft 365 service health - Microsoft 365 Enterprise | Microsoft Learn
If the behavior is happening on various users and sites/libraries, then it is suggested to raise a free Microsoft 365 Business support ticket from Admin Center so that the escalated engineers there will collect HAR logs from the tenant backend and investigate further for you and your company. Let admin follow: Get support - Microsoft 365 admin | Microsoft Learn
Meanwhile, I will keep your thread open and also monitor in the community to share with you once I get any updated information about such a situation.
Please correct me if I made any misunderstanding or if there have anything else I can do for you.
Your patience is highly appreciated. Hope you a nice day and stay safe!
Best Regards,
Mia