This can happen if GPS signal quality is weak and therefore accuracy is low. To understand the accuracy observe the blue circle around your location blob. The bigger the blue area the lower the location accuracy. If the accuracy is worse than 100 meters then no tasks will be activated.

To fix it you need to make sure there is good satellite reception. If you are indoors, move outdoors, if you are close to tall buildings or on narrow street, move to wider street or open place. If you are in deep forest move to open places.

When building games avoid placing tasks into tight locations. If you absolutely need to do it, make the task radius larger. It will not guarantee the activation but might make it easier.