java.lang.IllegalStateException: Unable to acquire application service. while launching Spring STS

I have installed Spring STS and have used it for about 6 months. A while ago, I tried to open Spring STS again to modify some code and I received this error:

java.lang.IllegalStateException: Unable to acquire application service. Ensure that the org.eclipse.core.runtime bundle is resolved and started (see config.ini).

Please help, I am absolutely not a Java expert, I was just working on this as a favor.