you have not provided very much detail on your test procedure.

The sparkplug may have carbon or oil around the electrode. This allows the electrical energy to reach the ground without creating a spark.

A briggs spark tester requires about 13,000 volts to jump the gap.

A cold engine will usually fire when voltage potential reaches about 8,000 volts.

A hot engine usually requires about 4,000 volts to continue running. these details are from the Briggs training videos.

More voltage is probably required depending on the sparkplug gap and condition of the sparkplug.

Thanks for the info. After inspecting the coil again I cleaned the mounting surface of the coil and the spark was good.