Hello! I am going to piggy-back on dockatiept's great response. Everything she mentioned is correct. In addition, we will occasionally see kids who are flat-footed prefer a toe-walking gait pattern as it offers them more stability. A pediatric PT, podiatrist or pediatric orthopedic specialist can help. Once the cause is identified (and sometimes it is as simple as that is their preferred walking pattern and we have to work to break that), we can work on solutions. Often that involves verbal cueing for "remember to put your heel to the ground", physical therapy, shoes/inserts that encourage heels to be on the ground. I recently was introduced to this brand of shoes that encourages avoidance of toe walking. Hope this helps!
https://ikiki.co/pages/toe-walking-and-ikiki-shoes?srsltid=AfmBOor-yRDWNDRdEZLxU0w_caVYEZIQ1QL9Cr_9kPoEtbu-0X7RwV1g

Here are some podiatry favorite brands of shoes for kids that are both fun and good for their feet:

Asics-great for kids an easy to get on/off with velcro straps
Stride Rite - they are at target now!
Puma Kids- I don't love for adults or older kids because they are too narrow BUT their kids shoes offer ample room
Plae
Ten Little
Keens (for sandals with protective toebox)
Kizik (they make cute kids shoes that don't need to be tied/untied which is great for getting out the door fast in the morning)

Those are just a few off the top of my head. Hope that helps!

I had an absolutely fantastic experience with Dr. Ashley Gordon at Restora Austin.