The sales module found at /web#home of our admin panel gives us the error at the bottom of the page. This is for version 11. We are at a loss of how to fix this. Any help is appreciated.

Here is a list of the modules we have installed: (I can't seem to fix the coloring...?)

• Import Inventory adjustment from CSV/XLS
• SEO-URL Redirect/Rewrite
• SEO-URL Redirect/Rewrite For Blog
• Product Variant Extra Price
• Odoo all import for Sales, Purchase, Invoice, Inventory,BOM, Pricelist, Payment, Bank Statement, Journal Entry, Picking, Product, Customer.
• CRM
• Project
• Inventory Management
• Manufacturing
• Sales Management
• Point of Sale
• Discuss
• Invoicing Management
• Accounting and Finance
• Website Builder
• eCommerce
• Purchase Management
• Employee Directory
• Contacts Directory
• Lost Messages Routing
• Odoo REST API
• Theme Clarico
• Odoo Webhook
• Website Webkul Addons
• Studio
• Email Marketing
• Calendar
• Blogs

Error:
Odoo Server Error

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 651, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 310, in _handle_exception
    raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
  File "/usr/lib/python3/dist-packages/odoo/tools/pycompat.py", line 87, in reraise
    raise value
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 693, in dispatch
    result = self._call_function(**self.params)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 342, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/odoo/service/model.py", line 97, in wrapper
    return f(dbname, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 335, in checked_call
    result = self.endpoint(*a, **kw)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 937, in __call__
    return self.method(*args, **kw)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 515, in response_wrap
    response = f(*args, **kw)
  File "/mnt/extra-addons/web/controllers/main.py", line 934, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/mnt/extra-addons/web/controllers/main.py", line 926, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/usr/lib/python3/dist-packages/odoo/api.py", line 687, in call_kw
    return call_kw_model(method, model, args, kwargs)
  File "/usr/lib/python3/dist-packages/odoo/api.py", line 672, in call_kw_model
    result = method(recs, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/odoo/models.py", line 1296, in load_views
    for [v_id, v_type] in views
  File "/usr/lib/python3/dist-packages/odoo/models.py", line 1296, in <dictcomp>
    for [v_id, v_type] in views
  File "/mnt/extra-addons/mail/models/mail_thread.py", line 374, in fields_view_get
    res = super(MailThread, self).fields_view_get(view_id=view_id, view_type=view_type, toolbar=toolbar, submenu=submenu)
  File "/usr/lib/python3/dist-packages/odoo/models.py", line 1382, in fields_view_get
    xarch, xfields = View.postprocess_and_fields(self._name, etree.fromstring(result['arch']), view_id)
  File "/mnt/extra-addons/base/ir/ir_ui_view.py", line 1064, in postprocess_and_fields
    self.raise_view_error(message, view_id)
  File "/mnt/extra-addons/base/ir/ir_ui_view.py", line 519, in raise_view_error
    raise ValueError(message)
ValueError: Field `system_seq` does not exist

Error context:
View `n/a`
[view_id: n/a, xml_id: n/a, model: n/a, parent_id: n/a]