According to the error message the certificate path is not trusted between NeoLoad and your Dynatrace. Do you use a self-signed certificate for your Dynatrace application? Or maybe your CA is unknown by the NeoLoad JVM and so not trusted.

In both cases you could add the Dynatrace certificate or CA in the NeoLoad JVM trustore following the procedure below:

Go to "$NeoLoad_install_dir>\jre\lib\security\" folder

Execute <java_install_dir>\bin\keytool.exe -import -alias dynatrace -file "c:\Users\<username>\Desktop\certificate.cer" -keystore cacerts -storepass changeit

where certificate.cer is either your Dynatrace certificate (it can downloaded from the browser) or your CA so they can be trusted.