[wp-trac] [WordPress Trac] #54938: Error 404 in WordPress after upgrading to v5.9

[WordPress Trac]

#54938: Error 404 in WordPress after upgrading to v5.9
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 Reporter:  somos         |       Owner:  (none)
     Type:  defect (bug)  |      Status:  assigned
 Priority:  normal        |   Milestone:  Awaiting Review
Component:  General       |     Version:  5.9
 Severity:  critical      |  Resolution:
 Keywords:  needs-patch   |     Focuses:
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Comment (by ipajen):

 Replying to [ticket:54938 somos]:
 > I got message 404 in all site when I upgraded to ver5.9

 One client of mine had the same problem, giving 404 on site but admin
 backend working fine, downgraded to latest 5.8.x and it worked fine again.
 I guessing in my clients case it’s the Helen Spa theme that’s is not
 compatible with 5.9 and making 404. Used the plug-in  WP Downgrade to make
 the downgrade.

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Ticket URL: <https://core.trac.wordpress.org/ticket/54938#comment:1>
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