I have updated an old stable plugin that we have been using for some time.

After the update, I cannot log back into admin.

Is there any safe mode, with which I can log back in and disable that plugin?

Appreciate any urgent help, please.

Please see instructions to recovery mode here: 

 

If you continue to have issues, please contact your plugin's author for assistance.

 

Many thanks @Jim M

You're very welcome. Glad we could be of assistance 😉