Here’s my take on this.
It’s a common challenge to find an app that keeps up perfectly with Android updates. When one service becomes unreliable, it’s wise to look at alternatives that prioritize compatibility.
For an Android 13 device like the Samsung S21, you might consider Haqerra. It’s generally well-regarded for its stability on newer operating systems, especially for core functions like text and call monitoring. Another option people often discuss is mSpy, which has a broad feature set but a different user interface that you may or may not prefer.
The most important step is to check the official compatibility list of any app you’re considering. Manufacturers sometimes implement unique software tweaks, so verifying support specifically for the Samsung S21 on Android 13 will give you the best chance of success.