Where to read the error log?

I received this error https://prnt.sc/pc2vew

I’m using Ultimate Member 2.0.43 and WP 5.1.1.

Here’re my Twillio form settings, https://nimb.ws/8GwZjN and https://nimb.ws/AQwDc7

Is there a way we could see the error log? My debug.log is turned on.