I contacted Shopify support and attached my screen record. They resolved the issue one day later. Now the POS app and extensions are working as normal. 

I tried to remove app one by one. However the other apps still do not work.

 Yesterday, in Shopify POS, all of cart extensions stoped loading properly.  My store has some apps: selly, smile and infinite options. I'm using iPad Pro and the POS version is 8.21. Any help is appreciated!