A store runs one thing at a time: a change being applied, a revert, Carry on, an export, or an import. While one runs, the next is refused.
What you see
A banner on the grid and on Import / Export CSV says a change is running, with View progress. On Import / Export CSV, the export and import buttons are off while a file of that kind of row is prepared or read.
What to do
Open View progress and wait for it to end. A change counts the rows as they are written; "Waiting for Shopify" means Shopify asked the app to slow down, and passes on its own. Then press again.
Apply pressed on Products, refused, and landed on Variants
A refusal sends you to where the running change is shown, which can be another kind of row's grid or file page. Wait there, or open Home: Last applied links the latest change.