@LauraGPA
Although not a fix for your particular issue you may wish to consider upgrading your Access data to SQL Server or SQL Server Express, which is free. As a general rule we recommend any client with 3 or more users to upgrade, allowing you to leverage the best of SQL Server and Access together.
For more information on upgrading just your data to SQL Server, check out:
https://support.office.com/en-us/article/migrate-an-access-database-to-sql-server-7bac0438-498a-4f53...
Please note: Just upgrading to SQL Server may not be enough, you may need to create views and stored procedures in order to get the performance you need, but it will be worth it in the end, since SQL Server is much more stable and has many other benefits over Access.