Hi Jose lara,
Greetings from Syncfusion Support.
We have validated your shared code snippet. There is no possibility to showing spinner in Scheduler events. Because it will be hidden in source level by default. So If you need to use Spinner after Schedule is rendered, Kindly follow the below sample.
Kindly try the above sample and let us know if you need any further assistance on this.
Regards, Balasubramanian S