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.