Here you can download the LGUP DLL for LG Aristo 2 LMX210MA from Metro PCS
The LGUP_X210MA.msi will install necessary files which enable LGUP tool to detect the model number and software version of your phone.
After installing the LGUP_X210MA.msi and LGUP Tool, You will be able to use LGUP to upgrade/downgrade the software of your LG Aristo 2 LMX210MA.
Download LGUP DLL for LG Aristo 2 LMX210MA
Need to download both files from above links.
How to install LGUP DLL
Just download the LGUP_X210MA.msi
Double click the LGUP_X210MA.msi to install LGUP DLL
Download LGUP_X210ma.zip, and unzip it, You will see LGUP_common-126.96.36.199.dll
Rename LGUP_common-188.8.131.52.dll into lgup_common.dll
Copy the lgup_common.dll into the folder C:\Program Files (x86)\LG Electronics\LGUP\model\common, and overwrite the existing DLL.