Dig "How to translate the EAP website to https"
And in any unclear situation with 404 error update permalinks
Layne answered on April 3rd 20 at 17:32
Can tell you 1000 reasons why that could be...
1) delete the htaccess file and re-generate it (Admin panel - Settings - Permalinks - Update)
2) Verify the certificate installation.
3) Check your server configuration. Sometimes there may be problems because of the hosting provider. I met with this situation in ISP Manager old version on one of the Belarusian hosting.
4) Update links in the database. For convenient replacement, use the Better Search Replace plugin