Problem with generated SSH public key files

I have tested many times.
Usually it is used PuTTYgen and it works without any issue.
 
Software SmartFTP is also perfectly working when connecting with such pairs but generated keys are not compliant with the control panels. It will not be within one line (keys are generated using SmrtFTP). So, manually changing will also not working when I set in one line.
 
My guess is only that pairs are not compliant.

I have a hard time to understand your problem. If you are having problems using the private key you generate with Puttygen, please send the private key file to support at smartftp.com

Thank you for your quick reply.
Please find ticket: 3336

It turned out the problem is with cPanel. It only supports OpenSSH and Putty public key files. It does not support the standardized RFC 4716 SSH key format.
 
To use the public key with cPanel, select the OpenSSH key format in the Public Key Export, Save As... dialog.

WHM will only accept:
 
1) OpenSSH format keys
2) Putty PPK keys
 
So, this is not an issue from SmartFTP.

In the Public Key Export, Save As... dialog. You can select the format. OpenSSH is one option.