If java isn't detected, TSplus will try to install JDK 11 by default.

Unfortunately, XP is very old now, and MS doesn't support it since a long time. 

Therefore, JDK doesn't support XP either since quite some time.

Please keep in mind that using XP today on a server isn't recommended. 

Solution: find a version of Java that supports XP and install it, then install TSplus.

It can be an old version of official Java, or an older version of JDK.