The following can cause low suction-
- A blockage in the vacuum system hose and/or vacuum system tools,
- One of your vacuum system pipes may have come apart or be cracked,
- A leak could be in the system somewhere,
- A dirty or blocked filter/ filter bag or
- A fault with the vacuum system power unit.
Always check all inlets for a blockage as unless the blockage is close to the power unit some of the other inlets may work fine.
If all the inlets seem low on suction there could be a blockage close or at the vacuum system power unit.