Group Tool Resorce Objects All Go Away When Availability Filter is On

Hello Formidable Team,
I am facing issues with resource allocation. The ultimate goal of this test is to see if a tool becomes unavailable once set to scheduled or unscheduled maintenance. But before I dealt with the maintenance side, I checked if I registered the resources properly.
If I start the allocation with the 'Filter by Available Resource' flag unchecked, I can see the three tools I registered for this Work Order (WO) available for selection. Once I check this option, all three tools go away. I opened only one VIM WO after registering the tools, so the unavailability does not come from other allocations. There is no EQUIPMENT WO open for tool repair or preventive maintenance. Why do they not show up in the allocation table?
At the resource navigator, we can select the calendar to be used by the Resource Group. I did not see any effect in choosing the two options loaded in the system, the default calendar and the Maintenance Calendar, which is 8:00 to 12:00, 13:00 to 17:00, Monday to Friday.
Regards,
Leibnitz