ERROR: SSL certificate problem (Push Bullet settings)

Hello,

Thank you for this superb plugin. It is the first I install to any new WP site.

I have all traffic to my single wp installation as https.
SSL works without problem, SSLShopper test is OK.
Certificate issued by Comodo.

But I get this error message when I want to setup Push Bullet feature:
ERROR: SSL certificate problem: unable to get local issuer certificate

Could you please look at the info bellow and help me?

Site is a fresh install of WP 4.9.2, today updated to 4.9.3

There is only one project management plugin bought at codecanyon. I dont think it is the cause.

I would very appreciate your helping me.

Thank you in advance,

Sincerely
eligoo

Info from Cerber tool:

[SERVER_SOFTWARE] => Apache/2.4.29 (Win64) OpenSSL/1.1.0g PHP/7.2.1
(Windows Server 2012R2)

[SSL_TLS_SNI] => https://www.danae.blue
[SSL_SERVER_S_DN_OU] => Domain Control Validated
[SSL_SERVER_S_DN_OU_1] => COMODO SSL
[SSL_SERVER_S_DN_CN] => https://www.danae.blue
[SSL_SERVER_I_DN_C] => GB
[SSL_SERVER_I_DN_ST] => Greater Manchester
[SSL_SERVER_I_DN_L] => Salford
[SSL_SERVER_I_DN_O] => COMODO CA Limited
[SSL_SERVER_I_DN_CN] => COMODO RSA Domain Validation Secure Server CA
[SSL_SERVER_SAN_DNS_0] => https://www.danae.blue
[SSL_SERVER_SAN_DNS_1] => danae.blue
[SSL_VERSION_INTERFACE] => mod_ssl/2.4.29
[SSL_VERSION_LIBRARY] => OpenSSL/1.1.0g
[SSL_PROTOCOL] => TLSv1.2
[SSL_SECURE_RENEG] => true
[SSL_COMPRESS_METHOD] => NULL
[SSL_CIPHER] => ECDHE-RSA-AES256-GCM-SHA384
[SSL_CIPHER_EXPORT] => false
[SSL_CIPHER_USEKEYSIZE] => 256
[SSL_CIPHER_ALGKEYSIZE] => 256
[SSL_CLIENT_VERIFY] => NONE
[SSL_SERVER_M_VERSION] => 3
[SSL_SERVER_M_SERIAL] => F51BEC5520505D2405100AB6FE85DC55
[SSL_SERVER_V_START] => Jan 31 00:00:00 2018 GMT
[SSL_SERVER_V_END] => Jan 31 23:59:59 2019 GMT
[SSL_SERVER_S_DN] => CN=www.danae.blue,OU=COMODO SSL,OU=Domain Control Validated
[SSL_SERVER_I_DN] => CN=COMODO RSA Domain Validation Secure Server CA,O=COMODO CA Limited,L=Salford,ST=Greater Manchester,C=GB
[SSL_SERVER_A_KEY] => rsaEncryption
[SSL_SERVER_A_SIG] => sha256WithRSAEncryption
[SSL_SESSION_ID] => 12149166d293d3dfe35c67f08f3a9295d4dcca109aa733caf0bbad167130b033
[SSL_SESSION_RESUMED] => Resumed