OK, managed to get the log... posted below.
---
16:34:01.749
Preparing to launch minecraft client for 1.16.5-forge-36.0.14
16:34:01.750
Prepared asset index
16:34:02.229
Have 2665 total files to check or download
16:34:02.234
Waiting for 2665 futures
16:34:02.564
Checking installations.
16:34:02.565
Minecraft client 1.16.5-forge-36.0.14 is ready to start.
16:34:02.566
Starting!
16:34:02.566
Nothing to download!
16:34:02.566
Downloading Java Runtime jre-legacy:8u51
16:34:03.570
Extracting 8 files!
16:34:04.058
Version does not support log configuration, will assume one plaintext entry per line
16:34:04.058
Installing versions!
16:34:04.591
2021-04-02 16:34:04,589 main WARN Advanced terminal features are not available in this environment
16:34:04.693
[16:34:04] [main/INFO] [cp.mo.mo.Launcher/MODLAUNCHER]: ModLauncher running: args [--username, Eddy_D, --version, 1.16.5-forge-36.0.14, --gameDir, C:\Users\rwill\AppData\Local\.ftba\instances\0baad395-0738-4e5f-ab33-7e805e5bf2f0, --assetsDir, C:\Users\rwill\AppData\Local\.ftba\bin\assets, --assetIndex, 1.16, --uuid, 2e3ed269b22e43c6823a2d8431d2ba9f, --accessToken, ????????, --userType, mojang, --versionType, release, --width, 1720, --height, 840, --launchTarget, fmlclient, --fml.forgeVersion, 36.0.14, --fml.mcVersion, 1.16.5, --fml.forgeGroup, net.minecraftforge, --fml.mcpVersion, 20210115.111550]
16:34:04.695
[16:34:04] [main/INFO] [cp.mo.mo.Launcher/MODLAUNCHER]: ModLauncher 8.0.9+86+master.3cf110c starting: java version 1.8.0_51 by Oracle Corporation
16:34:04.707
[16:34:04] [main/WARN] [cp.mo.mo.SecureJarHandler/]: LEGACY JDK DETECTED, SECURED JAR HANDLING DISABLED
16:34:05.001
[16:34:05] [main/INFO] [ne.mi.fm.lo.FixSSL/CORE]: Added Lets Encrypt root certificates as additional trust
16:34:05.033
[16:34:05] [main/INFO] [mixin/]: SpongePowered MIXIN Subsystem Version=0.8.2 Source=file:/C:/Users/rwill/AppData/Local/.ftba/bin/libraries/org/spongepowered/mixin/0.8.2/mixin-0.8.2.jar Service=ModLauncher Env=CLIENT
16:34:05.430
[16:34:05] [main/FATAL] [ne.mi.fm.lo.FMLCommonLaunchHandler/CORE]: Failed to find Minecraft resource version 1.16.5-20210115.111550 at C:\Users\rwill\AppData\Local\.ftba\bin\libraries\net\minecraftforge\forge\1.16.5-36.0.14\forge-1.16.5-36.0.14-client.jar
16:34:05.430
Exception in thread "main" [16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: java.lang.RuntimeException: Missing minecraft resource!
16:34:05.430
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at net.minecraftforge.fml.loading.FMLCommonLaunchHandler.lambda$validatePaths$4(FMLCommonLaunchHandler.java:124)
16:34:05.431
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at net.minecraftforge.fml.loading.FMLCommonLaunchHandler$$Lambda$166/79782883.accept(Unknown Source)
16:34:05.431
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
16:34:05.431
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
16:34:05.431
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at net.minecraftforge.fml.loading.FMLCommonLaunchHandler.validatePaths(FMLCommonLaunchHandler.java:121)
16:34:05.432
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at net.minecraftforge.fml.loading.FMLLoader.setupLaunchHandler(FMLLoader.java:202)
16:34:05.432
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at net.minecraftforge.fml.loading.FMLServiceProvider.initialize(FMLServiceProvider.java:94)
16:34:05.432
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at cpw.mods.modlauncher.TransformationServiceDecorator.onInitialize(TransformationServiceDecorator.java:68)
16:34:05.432
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at cpw.mods.modlauncher.TransformationServicesHandler.lambda$initialiseTransformationServices$7(TransformationServicesHandler.java:107)
16:34:05.432
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at cpw.mods.modlauncher.TransformationServicesHandler$$Lambda$93/239372207.accept(Unknown Source)
16:34:05.433
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at java.util.HashMap$Values.forEach(HashMap.java:972)
16:34:05.433
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at cpw.mods.modlauncher.TransformationServicesHandler.initialiseTransformationServices(TransformationServicesHandler.java:107)
16:34:05.433
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at cpw.mods.modlauncher.TransformationServicesHandler.initializeTransformationServices(TransformationServicesHandler.java:59)
16:34:05.434
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at cpw.mods.modlauncher.Launcher.run(Launcher.java:76)
16:34:05.434
[16:34:05] [main/INFO] [STDERR/]: [java.lang.ThreadGroup:uncaughtException:1052]: at cpw.mods.modlauncher.Launcher.main(Launcher.java:66)
16:34:06.034
Process crashed with exit code 1
(wow, minecraft log does not make it easy to cut-n-paste)