The workflow gets "stuck" because Business Central's standard "Workflow User Group" approval doesn't automatically handle sequential tiers based on amount within a single step.
Implement multiple approval steps in your workflow. Each step should have specific conditions for the PO amount (< £10k, > £10k & <= £250k, > £250k) and use Approver Type: Approver with correctly configured Approval User Setup (defining who approves whom in the hierarchy).
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