Before throwing my old Firefox off the computer and reinstalling the same version (78.10), Everything worked fine. but the old Firefox had some issues.  It would crash sometimes and there were some security issues.  Since reinstallation it doesn't crash but now it won't play Netflix or Amazon movies.   
    I went to Firefox listing of crash reports.  Below is a copy of one of them:

I just reinstalled Firefox. It is up to date and is my default browser. It won't play movies on Netflix or Amazon. I get a thin yellow strip at the top of the movie window saying that WidevineCdm crashed. This happens every time I try to play a Netflix movie. Before throwing my old Firefox off the computer and reinstalling the same version (78.10), Everything worked fine. but the old Firefox had some issues. It would crash sometimes and there were some security issues. Since reinstallation it doesn't crash but now it won't play Netflix or Amazon movies. I went to Firefox listing of crash reports. Below is a copy of one of them: Signature mozilla::gmp::GMPChild::ProcessingError More Reports Search UUID 54cb0271-952f-458c-9003-fa1530210425 Date Processed 2021-04-25 15:09:10 UTC Uptime 0 seconds Install Age 270,786 seconds since version was first installed (3 days, 3 hours and 13 minutes) Install Time 2021-04-20 13:06:53 Product Firefox Release Channel esr Version 78.10.0esr Build ID 20210412162915 (2021-04-12) Buildhub data OS OS X 10.9 OS Version 10.9.5 13F1911 Build Architecture amd64 CPU Info family 6 model 42 stepping 7 CPU Count 4 Adapter Vendor ID Advanced Micro Devices, Inc. [AMD/ATI] (0x1002) Adapter Device ID Whistler [Radeon HD 6630M/6650M/6750M/7670M/7690M] (0x6741) Startup Crash False Process Type plugin (WidevineCdm, ver: 4.10.2209.1, filename: widevinecdm) MOZ_CRASH Reason (Sanitized) MOZ_CRASH(aborting because of MsgProcessingError) Crash Reason EXC_BAD_ACCESS / KERN_INVALID_ADDRESS Crash Address 0x0 Available Physical Memory 1,091,334,144 bytes (1.09 GB) EMCheckCompatibility False App Notes FP(D00-L1000-W00000000-T000) WR? WR- OMTP? OMTP- GL Layers? GL Context? GL Context+ GL Layers+ Processor Notes processor_ip-172-31-8-93_us-west-2_compute_internal_7; ProcessorPipeline; non-integer value of "SecondsSinceLastCrash" Crashing Thread (0) Frame Module Signature Source Trust 0 XUL mozilla::gmp::GMPChild::ProcessingError(mozilla::ipc::HasResultCodes::Result, char const*) dom/media/gmp/GMPChild.cpp:585 context 1 XUL mozilla::ipc::IPCResult::Fail(mozilla::NotNull<mozilla::ipc::IProtocol*>, char const*, char const*) ipc/glue/ProtocolUtils.cpp:58 scan 2 XUL CrashReporter::AnnotateCrashReport(CrashReporter::Annotation, nsTSubstring<char> const&) toolkit/crashreporter/nsExceptionHandler.cpp:2443 scan 3 XUL mozilla::gmp::GMPChild::AnswerStartPlugin(nsTString<char16_t> const&) dom/media/gmp/GMPChild.cpp:543 scan 4 libmozglue.dylib mozilla::TimeStamp::Now(bool) mozglue/misc/TimeStamp_darwin.cpp:145 scan 5 XUL Pickle::EndRead(PickleIterator&, unsigned int) const ipc/chromium/src/base/pickle.cc:462 scan 6 XUL mozilla::gmp::PGMPChild::OnCallReceived(IPC::Message const&, IPC::Message*&) ipc/ipdl/PGMPChild.cpp:650 scan 7 XUL mozilla::ipc::MessageChannel::DispatchInterruptMessage(mozilla::ipc::ActorLifecycleProxy*, IPC::Message&&, unsigned long) ipc/glue/MessageChannel.cpp:2222 scan 8 XUL mozilla::ipc::MessageChannel::DispatchMessage(IPC::Message&&) ipc/glue/MessageChannel.cpp:2112 scan 9 libsystem_pthread.dylib _pthread_mutex_lock scan 10 libsystem_pthread.dylib _pthread_cond_updateval scan 11 libsystem_pthread.dylib __mtx_droplock scan 12 libsystem_pthread.dylib pthread_mutex_unlock scan 13 libsystem_pthread.dylib pthread_cond_destroy scan 14 libsystem_pthread.dylib __mtx_droplock scan 15 libsystem_pthread.dylib _pthread_mutex_lock scan 16 XUL mozilla::ipc::MessageChannel::MessageTask::Run() ipc/glue/MessageChannel.cpp:1993 scan 17 XUL <name omitted> ipc/chromium/src/base/message_loop.cc:523 scan 18 XUL <name omitted> ipc/chromium/src/base/message_pump_default.cc:35 scan 19 XUL empty_buffer (.llvm.6195693555896016987) scan 20 XUL MessageLoop::Run() ipc/chromium/src/base/message_loop.cc:290 scan 21 XUL XRE_InitChildProcess(int, char**, XREChildData const*)