Always getting error code in JMeter for missing Alias in certificate

I have a problem when loading a client-side certificate using Jmeter. I tried everything including editing system.properties file, with these lines:

javax.net.ssl.keyStoreType=pkcs12 or jks  
javax.net.ssl.keyStore=/path/to/your/jsk keystore or .p12 certificate
javax.net.ssl.keyStorePassword=your certificate or keystore password 

Then importing certificate manually through SSL manager and manually typing password, nothing works.

I always have this error:

javax.net.ssl.SSLException: java.lang.IllegalArgumentException: No certificate found for alias:'mykey'
    at sun.security.ssl.Alerts.getSSLException(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.handleException(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
    at org.apache.http.conn.ssl.SSLConnectionSocketFactory.createLayeredSocket(SSLConnectionSocketFactory.java:404)
    at .....

Alias is there, as print from certificate is showing: Keystore type: PKCS12 Keystore provider: SUN

Your keystore contains 1 entry

Alias name: mykey Creation date: Sep 27, 2019 Entry type: trustedCertEntry

What could be causing Jmeter to fail reading the certificate? Has anyone done something like this before?