The "Reached max execution time limit" error message means Finale cannot updated all the Shopify SKUs in its allocated time. See screenshot below.
Shopify's API only allows the Finale integration make a maximum of 2 requests per second. It takes at least 2 requests to update a single SKU on Shopify, meaning that it will start falling behind whenever the number of SKUs needing updated exceeds 1500 within a 25 minute period.
If you see that the push stock task is reaching max execution time consistently, that means that too many SKUs need updated, reducing the number of SKUs mapped to Shopify will help resolve the issue.
Here is a link to the documentation that explains this limit.
If you are still experiencing the error message after eliminating unneeded product mappings, you may need to upgrade to Shopify Plus to enable you to double the rate limit.
That will allow to to double the number of skus you need to update every 25 minutes is less than 3000 (double the previously mentioned limit).