Shopify has a rate limit that takes effect when a store has 50.000 product variants. After this threshold is reached, no more than 1000 new variants can be created per day. This causes the error:
"Shopify daily Variant import limit reached" or "Daily variant limit reached."
The published collection will stop in the AOP APP, the items will be put to pending status in the queue, and will once the time has refreshed, automatically the publishing continue. No need to republish again. You have an option as well to abort the pending in queue just click on the drop-down option beside the publish in progress button and choose abort.
Upgrading to the Shopify Plus plan will remove the daily variant limitation
Reference: Shopify Help Article: Adding variants
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