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@muma, what you pasted was incomplete; it was missing the intermediate certificate. This is what @JuergenAuer and @Osiris both noticed, and I can also confirm it.
What method did you use to obtain the certificate that you pasted this way? Maybe it provided some additional information elsewhere that you didn't end up using?
"private key" and "certificate" is not the same as "private key", "certificate" and "intermediate certificate" though.
Most "SSL upload" features support a certificate chain (which is the end leaf certificate plus intermediate certificate) as "certificate".
Unfortunately, you haven't answered the question about how you got the certificate in the first place, so no idea where you might be able to find the intermediate provided by the ACME client you've used.
Append/paste the contents of the intermediate certificate file to the bottom of your certificate file (being sure to leave a blank line between the two certificates).