Sometimes, when a pool is fitted with flexible PVC, aka, TigerFlex, the installers used barbed fittings that go inside and put hose clamps on them. These invariably leak because TigerFlex isn't designed for inside fitting.
Instead, remove the barbed fitting, and replace it with a glued-on Schedule 40 fitting, just like you'd use on hard PVC. For adaptability, I'd glue a threaded fitting on the TigerFlex, either M or F, and then attach the rest of the plumbing to it.

When my pool was initially installed, they used TigerFlex and internal barbed fittings and it was leaking as soon as they drove off. I then replaced all the fittings with glued-on Sched 40 and they were never a leak source again.