Note: There's an order when loading the mib into a mib browser.
Please follow the instructions regarding the order in which you load the MIBs. Note that for the PDU3VSR6L1530 you will not require the TRIPPLITE_PRODUCTS.MIB, but if your MIB browser is not file-limited, feel free to include it.
https://www.tripplite.com/shared/software/Firmware/WEBCARDLX%20MIB%20Instructions.pdf