Most likely you're running into the documented issue mentioned in this blog:
community.dynamics.com/.../microsoft-dynamics-gp-fall-2021---upgrading-the-web-client
We've added the fix to this issue in the Jan 2022 hotfix for Dynamics GP 18.4, which is the 'MicrosoftDynamicsGP18-KB4576805-ENU.msp' patch for 18.4.1434.
mbs2.microsoft.com/.../
The issue is to do with the Web Client Runtime feature we install with Dynamics GP desktop that Web Client is pointed at, specifically the 'WebClient' folder it puts into the Dynamics GP desktop directory, needed in order to use Web Client.
If you're not currently on 18.4.1434 or later and aren't able to upgrade right now, either of these two workarounds should resolve the issue as well:
#1:
a. Download the ‘MDGPFALL2020_DVD_ENUS,zip’ media from this link:
mbs2.microsoft.com/.../downloadfile.aspx
b. Extract this DVD and then use it to install Dynamics GP at the 18.3 version. When you install GP 18.3, you only need to select the ‘Web Client Runtime’ feature, that’s all we need.
c. When Dynamics GP 18.3 is installed, we only need to go into the GP 18.3 directory and make a copy of the existing ‘WebClient’ folder.
d. Then, take that 18.3 ‘WebClient’ folder and put it in the Dynamics GP 18.4 directory that Web Client is pointing at, replacing the existing ‘WebClient’ folder that will be present.
e. Launch Web Client for Dynamics GP 18.4 and verify that the menus now show as expected.
***NOTE: If you're not sure which Dynamics GP directory Web Client is pointed at, on the server that Web Client is installed onto, browse to C:\Program Files\Microsoft Dynamics\GP Web Components\SessionCentral\ and open the TenantConfiguration.xml file in NotePad. In this file you'll see the path to the GP directory, Dynamics.set and Dex.ini files for Dynamics GP, that Web Client is using. >> This is the only GP directory you need to change the 'WebClient' folder in.
Let me know if this isn't what you're seeing or didn't resolve for you.
Thanks,