What to do when the erection doesn’t start automatically

Hi,

So frustrating, have started having some issues where my erection isn’t immediately starting. Have take cialis for years and dosage started to have less effect so went from 5mg daily with 10mg for sexual activity days. But it started to cause some flushing so urologist suggested going to 15mg. Same on and off again issue with flushing and when I feel it might happen I just can’t start to get erect. Will take and hour or more with partner and multiple efforts and stimulations before I can start. Driving me crazy and making me feel like I’m failing.