Launcher fails to download 1.15 jar file

Launcher failed to download file 1.15.jar. The load-bar shows 33.35 MB loaded out of 66.7 (exactly half), then it times out after a few minutes. I was playing 1.14 (Java) just this morniing, and then shut down my computer. When I restarted the game later this afternoon, it tried to update to 1.15 and got only so far, and then hanged. Repeated attempts all have the same result.