In the Java version of MC, players need to right click an already charged respawn anchor to set a respawn point. This is contrary to the Bedrock version, where a respawn point is set by the act of charging the respawn anchor.

Repro

• Create a New World in Creative Mode.
• Grab Respawn Anchor and Glowstone from the Creative Inventory.
• Go to the Nether
• Place down the Respawn Anchor.
• Use Glowstone on the Respawn Anchor.
• Right click the Respawn anchor with an empty hand
• Observe that the respawn point is now set.