Cause of the issue:
The reason for this error"Please make sure the request URI is correct" could be not having the authorization to access the ping service in the SAP system and this error is written from the HTTP response 403.

To resolve this issue:
1. First of all please make sure that all the connection parameters are correct.
2. After that try to check if the same connection parameters work fine with the browser or postman.
3. If same connection parameters work fine with the browser or postman then check if the service /sap/bc/ping is active in the SAP system or not. 
There are two ways to checkthe service /sap/bc/ping is active in the SAP systemor not. 
I) Try and check the service /sap/bc/ping in the postman and see if the service is active/reached successfully in the SAP system.
For example: 

-String.valueOf(this.privateHostName) + ":" + this.privatePort +  "/sap/bc/ping"
-https://hostname:port/sap/bc/ping

II) Try to connect to /sap/bc/ping using the curl command.
For example:
-curl https://hostname:port/sap/bc/ping

4. If the ping service is not active(An error"403 forbidden - Service cannot be reached" is faced in postman or curl command line), the reason for this error"403 forbidden - Service cannot be reached" is due to not having the authorization to access the ping service and then this error in the BusinesStudio is returned as "please make sure the request URI is correct" as the error is from the HTTP response 403. 

5. To resolve this issue please go to SAP transaction SMICM and make sure that the ping service service(/sap/bc/ping) is active in the SAP system. If it is not active, right-click on the service and activate the service and execute the same curl command or test with the postman. If the curl or postman result is successful then please do a test connection from the BusinesStudio and let us know the result.