Required inputs not present — required inputs are marked with a red asterisk next to the field name. Scan every card, including inside branches (e.g. an If/Else), for a missing value. Any invalid card typically shows a red title.

Invalid isolated method — this alert can appear on several or even all cards in a flow. It usually results from a field mistakenly mapped from the right to the left. Turn on the X-Ray view (button at the right of the toolbar above the flow) to help locate it. Example: a Math Add card summing two prior cards' outputs — if you drag the Math Add card to the left of one of its own source cards, Invalid isolated method alerts appear across the flow; moving it back after both source cards clears them.

Invalid fields — the "Some fields are invalid" alert fires when a field is mapped from inside a branch to a card outside that branch (e.g. mapping the False branch of an If/Else to a later card). That field simply doesn't exist if the other branch runs instead. Fix it by moving the destination card inside the same branch, or by using branch Outputs to assign a value from each branch that does carry forward.

Invalid error handling — a flow with invalid error handling can't be saved or executed at all. Example: choosing the Run another flow error-handling option for a card but never selecting the helper flow the error details should return to.

→ Chasing an "Invalid isolated method" alert on the wrong card. The alert can surface on many cards at once even though the actual mistake — a field mapped right-to-left, or a card dragged out of execution order — lives on just one of them. Turn on X-Ray before you start guessing.