Some Ricoh printer models have issues handling SNMPv2 requests. If you're certain SNMP is enabled on your printer, but neither Lansweeper nor Lansweeper's Devicetester tool is able to access SNMP, try running Devicetester with just SNMPv1.
If SNMP access works under this setup, you can modify your SNMP credential within Lansweeper to only use SNMPv1 as well and rescan your problem printers. Check Use SNMP(v1) and uncheck Use SNMP(v2) for your SNMP credential. General instructions for scanning network devices can be found in this knowledge base article.