@fairymemay Can you Show us the Loop or the Entire Workflow ? Since maybe you are invoking Excel Application Scope again and again in a loop, it may be giving out the error.
Is the Loop really needed outside the Excel Scope ? If so, some posts related to the Error that you receive may be able to help fix the issue. One such post is below :
Check the below post and let us know if it as able to solve the issue :