When a supplier is inactive, you won't see them in the suppliers' list anymore. However, the supplier has not been deleted and can be reactivated through these steps:
1. Go to the Suppliers Management page;
2. Click on Show filters, type the supplier's name, and choose Active - "No" → Filter;
3. Select the supplier you want to make active again → click on the Edit button
→ press the Update button.
Now the supplier is active and available.