New flat insoles are usually easy to adjust to but an insole with an arch support or medial posting can take several weeks to adjust to. The bigger the changes in arch position the longer that period often is. Can be uncomfortable.
Consider easing yourself into a pair, by putting them in shoes for a couple of hours and then set those shoes aside. Build your tolerance by 2 hours daily.
All insoles will take up room in your footwear, so factor this in when deciding on which shoes will have the insoles.
2. Achilles tendonitis