This Speedtest 1.14 version will not run on any macOS prior to Mojave 10.14, even though it states compatible w macOS 10.11 (El Capitan) or higher. Look on the Appstore, ton of reviews stating the same, so not isolated. Also, this app is now listed twice on MU, see this page https://www.macupdate.com/app/mac/52710/speedtest-by-ookla