nRF Cloud AGPS Sample - Can't load using newtmgr

I was able to compile the nRF Cloud AGPS sample but when I try to execute the newtmgr image upload after entering DFU mode I get an Error 3. After trying this a several of times (doing different things) I then thought I could update the binary from the link provided but wasn’t sure how to do that. Do I rename the downloaded nrf_cloud_agps_bb259bf.bin to app_update.bin in the build/zephyr directory?
Here is the end of the compile and where I got the newtmgr error. If you’d like to see more of the compile I can provide that:

Call Stack (most recent call first):
  C:/ncs/bootloader/mcuboot/zephyr/CMakeLists.txt:1 (include)

CMake Warning at C:/ncs/zephyr/CMakeLists.txt:1379 (message):
  __ASSERT() statements are globally ENABLED

-- Configuring done
-- Generating done
-- Build files have been written to: C:/ncs/nrf/samples/nrf9160/nrf_cloud_agps/build
[9/209] Performing build step for 'mcuboot_subimage'
Memory region         Used Size  Region Size  %age Used
           FLASH:       42280 B        48 KB     86.02%
        IDT_LIST:          72 B         2 KB      3.52%
[249/249] Linking C executable zephyr\zephyr.elf
[188/193] Linking C executable zephyr\zephyr_prebuilt.elf
           FLASH:       32256 B        48 KB     65.63%
            SRAM:        5488 B        64 KB      8.37%
[193/193] Linking C executable zephyr\zephyr.elf
Memory region         Used Size  Region Size  %age Used
           FLASH:      149092 B     441856 B     33.74%
            SRAM:       43000 B       128 KB     32.81%
        IDT_LIST:         120 B         2 KB      5.86%
[209/209] Generating zephyr/merged.hex
PS C:\ncs\nrf\samples\nrf9160\nrf_cloud_agps> newtmgr conn add serial type=serial connstring="dev=COM20,baud=1000000"
Connection profile serial successfully added
PS C:\ncs\nrf\samples\nrf9160\nrf_cloud_agps> newtmgr -c serial image upload build/zephyr/app_update.bin
 0 / 199092 [----------------------------------------------------------------------------------------------------------------------------------------]   0.00%Error: 3

Any help would be appreciated. Thank you, Steve D.

I added the configuration commands you provided (see below) at the bottom of the prj.conf. I just noticed when I went back to look at what I added and even though I saved it it has the green bar saying that the configuration lines are pending. I fiddled around and now the green bar between the numbers and the config lines is gone, but have the config commands staged and their seems to be a separate path on the source control. When I looked this up I think it wants me to commit, but when I enter “commit” it wants me to log into git with name and password. I didn’t do that because I felt it was going to change this not just in my build. What would you suggest?

What I added to the prj.conf:

CONFIG_NRF_CLOUD_CLIENT_ID_PREFIX="feather-"

# Enable Zephyr application to be booted by MCUboot
CONFIG_BOOTLOADER_MCUBOOT=y

# COEX0 is used to enable the GPS LNA, but it has to be configured to do so.
CONFIG_NRF9160_GPS_SET_COEX0=y
CONFIG_NRF9160_GPS_COEX0_STRING="AT%XCOEX0=1,1,1565,1586"

Yes. Here it is:

PS C:\ncs\nrf> git status
HEAD detached from bb259bfa
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   samples/nrf9160/nrf_cloud_agps/prj.conf

no changes added to commit (use "git add" and/or "git commit -a")
PS C:\ncs\nrf> git log -n 1
commit a83f2e623fe81f0eb3873f0138d32c10eb8b8d59 (HEAD)
Author: Steve Doroff <Steve.Doroff@gmail.com>
Date:   Mon Nov 2 11:15:17 2020 -0500

    Add nrf prefix
PS C:\ncs\nrf>