If the server is unable to load and the console is stating [INFO Error: Unable to access jarfile] then the server jar it is trying to access is either not in the correct location or has been removed.
If this is a custom installation please make sure that the server jar has been uploaded to the servers jar folder - NOT the base directory as it would be for a localhost etc.. - and that it is named correctly. For simplicity and to make sure the panel works correctly with it is recommended to name the custom file custom_server.jar (all lowercase), and to use the Custom Server JAR option on the jar list.
Otherwise, make sure that the name of the jar file in the text field on the control panel matches the name of the file in the jar folder - this is case-sensitive and should include the file extension (such as `server.jar`).
If this is using one of the options on our 1-click install list please log into the server files and delete the jar folder, then restart the server - this will force reinstall that option. If this does not help please submit a support ticket and we will resolve this ASAP.