Expired certificate? Why can't I connect to mqtt.googleapis.com?

Hello, how are you doing?

I come to comment on the problem I am having to connect my MKR GSM 1400 board. It turns out that I am trying to connect to GCloud Iot Core through MQTT and it seems that the MKRGSM library has some of its certificates expired. These certificates can be found here.

In the GCloud documentation we can find the certificates to connect and not have problems, the problem arises when I download the file and it does not have the uint8_t format.

Can somebody help me? I've been with this problem for days.

Attempting to connect to MQTT broker: mqtt.googleapis.com 
AT+CCLK?

+CCLK: "21/10/08,19:24:53+08"

OK
AT+USECMNG=0,0,"AddTrust_External_CA_Root",1082
>
+USECMNG: 0,0,"AddTrust_External_CA_Root","1d3554048578b03f42424dbf20730a3f"

OK
AT+USECMNG=0,0,"Baltimore_CyberTrust_Root",891
>
+USECMNG: 0,0,"Baltimore_CyberTrust_Root","acb694a59c17e0d791529bb19706a6e4"

OK
AT+USECMNG=0,0,"COMODO_RSA_Certification_Authority",1500
>
+USECMNG: 0,0,"COMODO_RSA_Certification_Authority","1b31b0714036cc143691adc43efdec18"

OK
AT+USECMNG=0,0,"DST_Root_CA_X3",846
>
+USECMNG: 0,0,"DST_Root_CA_X3","410352dc0ff7501b16f0028eba6f45c5"

OK
AT+USECMNG=0,0,"DigiCert_High_Assurance_EV_Root_CA",969
>
+USECMNG: 0,0,"DigiCert_High_Assurance_EV_Root_CA","d474de575c39b2d39c8583c5c065498a"

OK
AT+USECMNG=0,0,"Entrust_Root_Certification_Authority",1173
>
+USECMNG: 0,0,"Entrust_Root_Certification_Authority","d6a5c3ed5ddd3e00c13d87921f1d3fe4"

OK
AT+USECMNG=0,0,"Equifax_Secure_Certificate_Authority",804
>
+USECMNG: 0,0,"Equifax_Secure_Certificate_Authority","67cb9dc013248a829bb2171ed11becd4"

OK
AT+USECMNG=0,0,"GeoTrust_Global_CA",856
>
+USECMNG: 0,0,"GeoTrust_Global_CA","f775ab29fb514eb7775eff053c998ef5"

OK
AT+USECMNG=0,0,"GeoTrust_Primary_Certification_Authority_G3",1026
>
+USECMNG: 0,0,"GeoTrust_Primary_Certification_Authority_G3","b5e83436c910445848706d2e83d4b805"

OK
AT+USECMNG=0,0,"GlobalSign",958
>
+USECMNG: 0,0,"GlobalSign","9414777e3e5efd8f30bd41b0cfe7d030"

OK
AT+USECMNG=0,0,"Go_Daddy_Root_Certificate_Authority_G2",969
>
+USECMNG: 0,0,"Go_Daddy_Root_Certificate_Authority_G2","803abc22c1e6fb8d9b3b274a321b9a01"

OK
AT+USECMNG=0,0,"VeriSign_Class_3_Public_Primary_Certification_Authority_G5",1239
>
+USECMNG: 0,0,"VeriSign_Class_3_Public_Primary_Certification_Authority_G5","cb17e431673ee209fe455793f30afa1c"

OK
AT+USECMNG=2,0,"AmazonRootCA1"

ERROR
AT+USECMNG=0,0,"Starfield_Services_Root_Certificate_Authority_G2",1011
>
+USECMNG: 0,0,"Starfield_Services_Root_Certificate_Authority_G2","173574af7b611cebf4f93ce2ee40f9a2"

OK
AT+USOCR=6

+USOCR: 0

OK
AT+USOSEC=0,1,0

OK
AT+USECPRF=0,0,1

OK
AT+USOCO=0,"mqtt.googleapis.com",8883

ERROR
AT+USOCL=0

ERROR

I seem to be having a similar issue with the AWS IoT Core example. It successfully connects to GSM but will not connect to the Broker.

In order to make all relevant information available to all who are interested in this subject, I'll share a link to the related discussion at:

https://github.com/arduino-libraries/MKRGSM/issues/137#issuecomment-951924999