You change the owner. It changes back, or never moves.

The owner never moves

1. A validation rule blocks the save. Fix: read the error on the page, then the validation rules on Lead.
2. The new owner cannot use leads. They need access to the Lead object. Fix: check their profile or permission sets. See sharing and list views.
3. The new owner is inactive. Salesforce will not give a record to an inactive user. Fix: pick an active user.

The owner moves back

1. A flow sets the owner on every save. Fix: see a flow overriding the rule.
2. A sync from another tool writes the owner. Fix: see a sync overwriting the owner.

Check it yourself

Change the owner on one test lead, then read its history.

SELECT OldValue, NewValue, CreatedById, CreatedDate FROM LeadHistory WHERE LeadId = '00Q...' AND Field = 'Owner'

An owner change can show as two rows, one with IDs and one with names. Look for a later change by a different user. Field history tracking must be on for Lead Owner. Owners that flip often are covered in ownership ping-pong.

The free scan checks your export for:

• more than one system setting the Lead owner
• flows that set the owner on every edit

Decide from what you see

• An error on the page: read it. A validation rule, access or an inactive user. Fix that.
• It saves, then a second history row appears seconds later. An automation moved it back. The user on that row names it.
• It saves and nothing else changes: the owner did move. Check the list view you are looking at.

A worked example

A made-up case: reassigning a lead to Priya fails with a message that Country is required. A validation rule asks for Country whenever the owner changes.

The owner is not the problem. Either the lead lacks a country, or the rule is too strict. Fill the country, or narrow the rule, then try again.

Steps

1. Change the owner on one test lead.
2. Note whether an error appears.
3. If it saves, read the history for a second row.
4. Match what you find to the lists above.