Home Depot Wi-Fi connection issues!

I am so frustrated with trying to connect my phone to Home Depot Guest Wi-Fi! Some times I go in and it connects just fine. Most of the time I can’t get cell service and I can’t connect to the Wi-Fi because my stupid phone keeps giving me the “Cannot verify server identity” over and over again! I am so sick of this and it’s a huge problem when you’re trying to run a buisness and need service while you’re at the store. Please help!