Clean your pump after your first use and every use after to avoid suction issues from blocked parts.
You can also check your pump’s assembly. Make sure all the parts are connected securely and well-sealed. Loose or improperly installed parts will lower the suction level. Assembling the pump just after disinfection when it is still moist can improve the suction level.
If you own multiple different 88 club Avent breast pump products, make sure you aren’t mixing the parts, and do not use parts from other brands.
For more information on proper pump assembly, go to the page for your product and search "How to assemble” or check the online user manual.