Make sure the phone is set to 2.4 G on the hotspot side.
Back when I had Spectrum Internet router here it had one SSID/PSK for both 2.4 and 5GHZ
My printer and smart switches would NOT connnect
My Raspberry Pi's would but... very flakey
Finally I pulled the Spectrum router and took it back to spectrum and told 'em where to shove it (Back into the re-stock room) (What you thought somethign else) And put in a lovely Archer 10 from TP-link.. Two Bands THREE SSID's and up to 3 PSK's (one for 2.4Ghz. one for 5Ghz (with the same or different PSKs) and one for "Guest" (pick a band and a differnet PSK) The printer locked on the smart outlet switches locked on. the Raspberry pi (The one that still uses Wi-Fi) locked on (the others will if I unplug them from the Router's lan ports) and all the computers lock on to either band. The only time I have issues is when I'm recording a new device that configures via Auto-AP type configuration (I connect my phone's ap to the device as though it was a router) the phone has to be connected to the same SSID as the device will connect to.. This is not your problem however as you don't connect the computer that way.
I'd make sure the phone is set to 2.4Ghz for the hotspot and simplify the SSID to get rid of any "Special" (not letters or numbers) in the SSID.