current IMAP and STMP settings for gmail?

Gmail IMAP Settings for Incoming Mail

To receive your Gmail messages on other devices, enter the following settings according to the directions for the specific application:

• Gmail IMAP server address: imap.gmail.com
• Gmail IMAP username: Your full Gmail address (for example, example@gmail.com)
• Gmail IMAP password: Your Gmail password (use an application-specific Gmail password if you enabled 2-step authentication for Gmail)
• Gmail IMAP port: 993
• Gmail IMAP TLS/SSL required: yes

Gmail SMTP Settings for Outgoing Mail

While setting up your client to receive Gmail messages, provide settings to allow it to send messages. Messages are sent using Simple Mail Transfer Protocol (SMTP) settings. You'll also need these SMTP settings to access Gmail with another mail client: 

• Gmail SMTP server address: smtp.gmail.com
• Gmail SMTP username: Your full Gmail address (for example, example@gmail.com)
• Gmail SMTP password: Your Gmail password
• Gmail SMTP port (TLS): 587
• Gmail SMTP port (SSL): 465
• Gmail SMTP TLS/SSL required: yes

Either TLS or SSL can be used, depending on your email client.

But see if this might be the problem...

Mac's Mail App is not as modern as iOS's Mail app, Many eMail providers now require a separate App Password different from your eMail password,  it may just need an App Password...

https://support.google.com/mail/answer/185833?hl=en-GB…